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README.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
<html><body>

<p><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://badge.fury.io/rb/sinatra"><img" rel="nofollow">https://badge.fury.io/rb/sinatra"><img src="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://badge.fury.io/rb/sinatra.svg" rel="nofollow">https://badge.fury.io/rb/sinatra.svg" alt="Gem Version"></a>
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/sinatra/sinatra/actions/workflows/test.yml"><img">https://github.com/sinatra/sinatra/actions/workflows/test.yml"><img src="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/sinatra/sinatra/actions/workflows/test.yml/badge.svg">https://github.com/sinatra/sinatra/actions/workflows/test.yml/badge.svg" alt="Testing"></a></p>

<p>Sinatra is a <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://en.wikipedia.org/wiki/Domain-specific_language">DSL</a" rel="nofollow">https://en.wikipedia.org/wiki/Domain-specific_language">DSL</a> for
quickly creating web applications in Ruby with minimal effort:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># myapp.rb</span>
<span class="nb">require</span> <span class="s1">'sinatra'</span>

<span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="s1">'Hello world!'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Install the gems needed:</p>

<div class="language-shell highlighter-rouge"><div class="highlight"><pre class="highlight"><code>gem <span class="nb">install </span>sinatra rackup puma
</code></pre></div></div>

<p>And run with:</p>

<div class="language-shell highlighter-rouge"><div class="highlight"><pre class="highlight"><code>ruby myapp.rb
</code></pre></div></div>

<p>View at: <a href="/deoxy?target=http%3A%2F%2Flocalhost%3A4567%2F">http://localhost:4567</a></p>

<p>The code you changed will not take effect until you restart the server.
Please restart the server every time you change or use a code reloader
like <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/alexch/rerun">rerun</a">https://github.com/alexch/rerun">rerun</a> or
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/jeremyevans/rack-unreloader">rack-unreloader</a>.</p">https://github.com/jeremyevans/rack-unreloader">rack-unreloader</a>.</p>

<p>It is recommended to also run <code>gem install puma</code>, which Sinatra will
pick up if available.</p>





<h2 id="routes">Routes</h2>

<p>In Sinatra, a route is an HTTP method paired with a URL-matching pattern.
Each route is associated with a block:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="o">..</span> <span class="n">show</span> <span class="n">something</span> <span class="o">..</span>
<span class="k">end</span>

<span class="n">post</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="o">..</span> <span class="n">create</span> <span class="n">something</span> <span class="o">..</span>
<span class="k">end</span>

<span class="n">put</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="o">..</span> <span class="n">replace</span> <span class="n">something</span> <span class="o">..</span>
<span class="k">end</span>

<span class="n">patch</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="o">..</span> <span class="n">modify</span> <span class="n">something</span> <span class="o">..</span>
<span class="k">end</span>

<span class="n">delete</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="o">..</span> <span class="n">annihilate</span> <span class="n">something</span> <span class="o">..</span>
<span class="k">end</span>

<span class="n">options</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="o">..</span> <span class="n">appease</span> <span class="n">something</span> <span class="o">..</span>
<span class="k">end</span>

<span class="n">link</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="o">..</span> <span class="n">affiliate</span> <span class="n">something</span> <span class="o">..</span>
<span class="k">end</span>

<span class="n">unlink</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="o">..</span> <span class="n">separate</span> <span class="n">something</span> <span class="o">..</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Routes are matched in the order they are defined. The first route that
matches the request is invoked.</p>

<p>Routes with trailing slashes are different from the ones without:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/foo'</span> <span class="k">do</span>
  <span class="c1"># Does not match "GET /foo/"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Route patterns may include named parameters, accessible via the
<code>params</code> hash:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/hello/:name'</span> <span class="k">do</span>
  <span class="c1"># matches "GET /hello/foo" and "GET /hello/bar"</span>
  <span class="c1"># params['name'] is 'foo' or 'bar'</span>
  <span class="s2">"Hello </span><span class="si">#{</span><span class="n">params</span><span class="p">[</span><span class="s1">'name'</span><span class="p">]</span><span class="si">}</span><span class="s2">!"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>You can also access named parameters via block parameters:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/hello/:name'</span> <span class="k">do</span> <span class="o">|</span><span class="n">n</span><span class="o">|</span>
  <span class="c1"># matches "GET /hello/foo" and "GET /hello/bar"</span>
  <span class="c1"># params['name'] is 'foo' or 'bar'</span>
  <span class="c1"># n stores params['name']</span>
  <span class="s2">"Hello </span><span class="si">#{</span><span class="n">n</span><span class="si">}</span><span class="s2">!"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Route patterns may also include splat (or wildcard) parameters, accessible
via the <code>params['splat']</code> array:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/say/*/to/*'</span> <span class="k">do</span>
  <span class="c1"># matches /say/hello/to/world</span>
  <span class="n">params</span><span class="p">[</span><span class="s1">'splat'</span><span class="p">]</span> <span class="c1"># =&gt; ["hello", "world"]</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/download/*.*'</span> <span class="k">do</span>
  <span class="c1"># matches /download/path/to/file.xml</span>
  <span class="n">params</span><span class="p">[</span><span class="s1">'splat'</span><span class="p">]</span> <span class="c1"># =&gt; ["path/to/file", "xml"]</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Or with block parameters:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/download/*.*'</span> <span class="k">do</span> <span class="o">|</span><span class="n">path</span><span class="p">,</span> <span class="n">ext</span><span class="o">|</span>
  <span class="p">[</span><span class="n">path</span><span class="p">,</span> <span class="n">ext</span><span class="p">]</span> <span class="c1"># =&gt; ["path/to/file", "xml"]</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Route matching with Regular Expressions:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="sr">/\/hello\/([\w]+)/</span> <span class="k">do</span>
  <span class="s2">"Hello, </span><span class="si">#{</span><span class="n">params</span><span class="p">[</span><span class="s1">'captures'</span><span class="p">].</span><span class="nf">first</span><span class="si">}</span><span class="s2">!"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Or with a block parameter:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="sr">%r{/hello/([</span><span class="se">\w</span><span class="sr">]+)}</span> <span class="k">do</span> <span class="o">|</span><span class="n">c</span><span class="o">|</span>
  <span class="c1"># Matches "GET /meta/hello/world", "GET /hello/world/1234" etc.</span>
  <span class="s2">"Hello, </span><span class="si">#{</span><span class="n">c</span><span class="si">}</span><span class="s2">!"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Route patterns may have optional parameters:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/posts/:format?'</span> <span class="k">do</span>
  <span class="c1"># matches "GET /posts/" and any extension "GET /posts/json", "GET /posts/xml" etc</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Routes may also utilize query parameters:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/posts'</span> <span class="k">do</span>
  <span class="c1"># matches "GET /posts?title=foo&amp;author=bar"</span>
  <span class="n">title</span> <span class="o">=</span> <span class="n">params</span><span class="p">[</span><span class="s1">'title'</span><span class="p">]</span>
  <span class="n">author</span> <span class="o">=</span> <span class="n">params</span><span class="p">[</span><span class="s1">'author'</span><span class="p">]</span>
  <span class="c1"># uses title and author variables; query is optional to the /posts route</span>
<span class="k">end</span>
</code></pre></div></div>

<p>By the way, unless you disable the path traversal attack protection (see
<a href="#configuring-attack-protection">below</a>), the request path might be modified before
matching against your routes.</p>

<p>You may customize the <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/sinatra/mustermann#readme">Mustermann</a">https://github.com/sinatra/mustermann#readme">Mustermann</a>
options used for a given route by passing in a <code>:mustermann_opts</code> hash:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'\A/posts\z'</span><span class="p">,</span> <span class="ss">:mustermann_opts</span> <span class="o">=&gt;</span> <span class="p">{</span> <span class="ss">:type</span> <span class="o">=&gt;</span> <span class="ss">:regexp</span><span class="p">,</span> <span class="ss">:check_anchors</span> <span class="o">=&gt;</span> <span class="kp">false</span> <span class="p">}</span> <span class="k">do</span>
  <span class="c1"># matches /posts exactly, with explicit anchoring</span>
  <span class="s2">"If you match an anchored pattern clap your hands!"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>It looks like a <a href="#conditions">condition</a>, but it isn’t one! These options will
be merged into the global <code>:mustermann_opts</code> hash described
<a href="#available-settings">below</a>.</p>

<h2 id="conditions">Conditions</h2>

<p>Routes may include a variety of matching conditions, such as the user agent:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/foo'</span><span class="p">,</span> <span class="ss">:agent</span> <span class="o">=&gt;</span> <span class="sr">/Songbird (\d\.\d)[\d\/]*?/</span> <span class="k">do</span>
  <span class="s2">"You're using Songbird version </span><span class="si">#{</span><span class="n">params</span><span class="p">[</span><span class="s1">'agent'</span><span class="p">][</span><span class="mi">0</span><span class="p">]</span><span class="si">}</span><span class="s2">"</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/foo'</span> <span class="k">do</span>
  <span class="c1"># Matches non-songbird browsers</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Other available conditions are <code>host_name</code> and <code>provides</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span><span class="p">,</span> <span class="ss">:host_name</span> <span class="o">=&gt;</span> <span class="sr">/^admin\./</span> <span class="k">do</span>
  <span class="s2">"Admin Area, Access denied!"</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/'</span><span class="p">,</span> <span class="ss">:provides</span> <span class="o">=&gt;</span> <span class="s1">'html'</span> <span class="k">do</span>
  <span class="n">haml</span> <span class="ss">:index</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/'</span><span class="p">,</span> <span class="ss">:provides</span> <span class="o">=&gt;</span> <span class="p">[</span><span class="s1">'rss'</span><span class="p">,</span> <span class="s1">'atom'</span><span class="p">,</span> <span class="s1">'xml'</span><span class="p">]</span> <span class="k">do</span>
  <span class="n">builder</span> <span class="ss">:feed</span>
<span class="k">end</span>
</code></pre></div></div>
<p><code>provides</code> searches the request’s Accept header.</p>

<p>You can easily define your own conditions:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span><span class="p">(</span><span class="ss">:probability</span><span class="p">)</span> <span class="p">{</span> <span class="o">|</span><span class="n">value</span><span class="o">|</span> <span class="n">condition</span> <span class="p">{</span> <span class="nb">rand</span> <span class="o">&lt;=</span> <span class="n">value</span> <span class="p">}</span> <span class="p">}</span>

<span class="n">get</span> <span class="s1">'/win_a_car'</span><span class="p">,</span> <span class="ss">:probability</span> <span class="o">=&gt;</span> <span class="mf">0.1</span> <span class="k">do</span>
  <span class="s2">"You won!"</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/win_a_car'</span> <span class="k">do</span>
  <span class="s2">"Sorry, you lost."</span>
<span class="k">end</span>
</code></pre></div></div>

<p>For a condition that takes multiple values use a splat:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span><span class="p">(</span><span class="ss">:auth</span><span class="p">)</span> <span class="k">do</span> <span class="o">|*</span><span class="n">roles</span><span class="o">|</span>   <span class="c1"># &lt;- notice the splat here</span>
  <span class="n">condition</span> <span class="k">do</span>
    <span class="k">unless</span> <span class="n">logged_in?</span> <span class="o">&amp;&amp;</span> <span class="n">roles</span><span class="p">.</span><span class="nf">any?</span> <span class="p">{</span><span class="o">|</span><span class="n">role</span><span class="o">|</span> <span class="n">current_user</span><span class="p">.</span><span class="nf">in_role?</span> <span class="n">role</span> <span class="p">}</span>
      <span class="n">redirect</span> <span class="s2">"/login/"</span><span class="p">,</span> <span class="mi">303</span>
    <span class="k">end</span>
  <span class="k">end</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s2">"/my/account/"</span><span class="p">,</span> <span class="ss">:auth</span> <span class="o">=&gt;</span> <span class="p">[</span><span class="ss">:user</span><span class="p">,</span> <span class="ss">:admin</span><span class="p">]</span> <span class="k">do</span>
  <span class="s2">"Your Account Details"</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s2">"/only/admin/"</span><span class="p">,</span> <span class="ss">:auth</span> <span class="o">=&gt;</span> <span class="ss">:admin</span> <span class="k">do</span>
  <span class="s2">"Only admins are allowed here!"</span>
<span class="k">end</span>
</code></pre></div></div>

<h2 id="return-values">Return Values</h2>

<p>The return value of a route block determines at least the response body
passed on to the HTTP client or at least the next middleware in the
Rack stack. Most commonly, this is a string, as in the above examples.
But other values are also accepted.</p>

<p>You can return an object that would either be a valid Rack response, Rack
body object or HTTP status code:</p>

<ul>
  <li>An Array with three elements: <code>[status (Integer), headers (Hash), response
body (responds to #each)]</code>
</li>
  <li>An Array with two elements: <code>[status (Integer), response body (responds to
#each)]</code>
</li>
  <li>An object that responds to <code>#each</code> and passes nothing but strings to
the given block</li>
  <li>A Integer representing the status code</li>
</ul>

<p>That way we can, for instance, easily implement a streaming example:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="nc">Stream</span>
  <span class="k">def</span> <span class="nf">each</span>
    <span class="mi">100</span><span class="p">.</span><span class="nf">times</span> <span class="p">{</span> <span class="o">|</span><span class="n">i</span><span class="o">|</span> <span class="k">yield</span> <span class="s2">"</span><span class="si">#{</span><span class="n">i</span><span class="si">}</span><span class="se">\n</span><span class="s2">"</span> <span class="p">}</span>
  <span class="k">end</span>
<span class="k">end</span>

<span class="n">get</span><span class="p">(</span><span class="s1">'/'</span><span class="p">)</span> <span class="p">{</span> <span class="no">Stream</span><span class="p">.</span><span class="nf">new</span> <span class="p">}</span>
</code></pre></div></div>

<p>You can also use the <code>stream</code> helper method (<a href="#streaming-responses">described below</a>) to reduce
boilerplate and embed the streaming logic in the route.</p>

<h2 id="custom-route-matchers">Custom Route Matchers</h2>

<p>As shown above, Sinatra ships with built-in support for using String
patterns and regular expressions as route matches. However, it does not
stop there. You can easily define your own matchers:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="nc">AllButPattern</span>
  <span class="k">def</span> <span class="nf">initialize</span><span class="p">(</span><span class="n">except</span><span class="p">)</span>
    <span class="vi">@except</span> <span class="o">=</span> <span class="n">except</span>
  <span class="k">end</span>

  <span class="k">def</span> <span class="nf">to_pattern</span><span class="p">(</span><span class="n">options</span><span class="p">)</span>
    <span class="k">return</span> <span class="nb">self</span>
  <span class="k">end</span>

  <span class="k">def</span> <span class="nf">params</span><span class="p">(</span><span class="n">route</span><span class="p">)</span>
    <span class="k">return</span> <span class="p">{}</span> <span class="k">unless</span> <span class="vi">@except</span> <span class="o">===</span> <span class="n">route</span>
  <span class="k">end</span>
<span class="k">end</span>

<span class="k">def</span> <span class="nf">all_but</span><span class="p">(</span><span class="n">pattern</span><span class="p">)</span>
  <span class="no">AllButPattern</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="n">pattern</span><span class="p">)</span>
<span class="k">end</span>

<span class="n">get</span> <span class="n">all_but</span><span class="p">(</span><span class="s2">"/index"</span><span class="p">)</span> <span class="k">do</span>
  <span class="c1"># ...</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Note that the above example might be over-engineered, as it can also be
expressed as:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="sr">/.*/</span> <span class="k">do</span>
  <span class="n">pass</span> <span class="k">if</span> <span class="n">request</span><span class="p">.</span><span class="nf">path_info</span> <span class="o">==</span> <span class="s2">"/index"</span>
  <span class="c1"># ...</span>
<span class="k">end</span>
</code></pre></div></div>

<h2 id="static-files">Static Files</h2>

<p>Static files are served from the <code>./public</code> directory. You can specify
a different location by setting the <code>:public_folder</code> option:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:public_folder</span><span class="p">,</span> <span class="n">__dir__</span> <span class="o">+</span> <span class="s1">'/static'</span>
</code></pre></div></div>

<p>Note that the public directory name is not included in the URL. A file
<code>./public/css/style.css</code> is made available as
<code>http://example.com/css/style.css</code>.</p>

<p>Use the <code>:static_cache_control</code> setting (see <a href="#cache-control">below</a>) to add
<code>Cache-Control</code> header info.</p>

<h2 id="views-templates">Views / Templates</h2>

<p>Each template language is exposed via its own rendering method. These
methods simply return a string:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">erb</span> <span class="ss">:index</span>
<span class="k">end</span>
</code></pre></div></div>

<p>This renders <code>views/index.erb</code>.</p>

<p>Instead of a template name, you can also just pass in the template content
directly:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">code</span> <span class="o">=</span> <span class="s2">"&lt;%= Time.now %&gt;"</span>
  <span class="n">erb</span> <span class="n">code</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Templates take a second argument, the options hash:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">erb</span> <span class="ss">:index</span><span class="p">,</span> <span class="ss">:layout</span> <span class="o">=&gt;</span> <span class="ss">:post</span>
<span class="k">end</span>
</code></pre></div></div>

<p>This will render <code>views/index.erb</code> embedded in the
<code>views/post.erb</code> (default is <code>views/layout.erb</code>, if it exists).</p>

<p>Any options not understood by Sinatra will be passed on to the template
engine:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">haml</span> <span class="ss">:index</span><span class="p">,</span> <span class="ss">:format</span> <span class="o">=&gt;</span> <span class="ss">:html5</span>
<span class="k">end</span>
</code></pre></div></div>

<p>You can also set options per template language in general:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:haml</span><span class="p">,</span> <span class="ss">:format</span> <span class="o">=&gt;</span> <span class="ss">:html5</span>

<span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">haml</span> <span class="ss">:index</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Options passed to the render method override options set via <code>set</code>.</p>

<p>Available Options:</p>

<dl>
  <dt>locals</dt>
  <dd>
    List of locals passed to the document. Handy with partials.
    Example: <tt>erb "&lt;%= foo %&gt;", :locals =&gt; {:foo =&gt; "bar"}</tt>
  </dd>

  <dt>default_encoding</dt>
  <dd>
    String encoding to use if uncertain. Defaults to
    <tt>settings.default_encoding</tt>.
  </dd>

  <dt>views</dt>
  <dd>
    Views folder to load templates from. Defaults to <tt>settings.views</tt>.
  </dd>

  <dt>layout</dt>
  <dd>
    Whether to use a layout (<tt>true</tt> or <tt>false</tt>). If it's a
    Symbol, specifies what template to use. Example:
    <tt>erb :index, :layout =&gt; !request.xhr?</tt>
  </dd>

  <dt>content_type</dt>
  <dd>
    Content-Type the template produces. Default depends on template language.
  </dd>

  <dt>scope</dt>
  <dd>
    Scope to render template under. Defaults to the application
    instance. If you change this, instance variables and helper methods
    will not be available.
  </dd>

  <dt>layout_engine</dt>
  <dd>
    Template engine to use for rendering the layout. Useful for
    languages that do not support layouts otherwise. Defaults to the
    engine used for the template. Example: <tt>set :rdoc, :layout_engine
    =&gt; :erb</tt>
  </dd>

  <dt>layout_options</dt>
  <dd>
    Special options only used for rendering the layout. Example:
    <tt>set :rdoc, :layout_options =&gt; { :views =&gt; 'views/layouts' }</tt>
  </dd>
</dl>

<p>Templates are assumed to be located directly under the <code>./views</code>
directory. To use a different views directory:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:views</span><span class="p">,</span> <span class="n">settings</span><span class="p">.</span><span class="nf">root</span> <span class="o">+</span> <span class="s1">'/templates'</span>
</code></pre></div></div>

<p>One important thing to remember is that you always have to reference
templates with symbols, even if they’re in a subdirectory (in this case,
use: <code>:'subdir/template'</code> or <code>'subdir/template'.to_sym</code>). You must use a
symbol because otherwise rendering methods will render any strings
passed to them directly.</p>

<h3 id="literal-templates">Literal Templates</h3>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">haml</span> <span class="s1">'%div.title Hello World'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Renders the template string. You can optionally specify <code>:path</code> and
<code>:line</code> for a clearer backtrace if there is a filesystem path or line
associated with that string:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">haml</span> <span class="s1">'%div.title Hello World'</span><span class="p">,</span> <span class="ss">:path</span> <span class="o">=&gt;</span> <span class="s1">'examples/file.haml'</span><span class="p">,</span> <span class="ss">:line</span> <span class="o">=&gt;</span> <span class="mi">3</span>
<span class="k">end</span>
</code></pre></div></div>

<h3 id="available-template-languages">Available Template Languages</h3>

<p>Some languages have multiple implementations. To specify what implementation
to use (and to be thread-safe), you should simply require it first:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'rdiscount'</span>
<span class="n">get</span><span class="p">(</span><span class="s1">'/'</span><span class="p">)</span> <span class="p">{</span> <span class="n">markdown</span> <span class="ss">:index</span> <span class="p">}</span>
</code></pre></div></div>

<h4 id="haml-templates">Haml Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"http://haml.info/" rel="nofollow">http://haml.info/" title="haml">haml</a></td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td><tt>.haml</tt></td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>haml :index, :format =&gt; :html5</tt></td>
  </tr>
</table>

<h4 id="erb-templates">Erb Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td>
      <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/jeremyevans/erubi">https://github.com/jeremyevans/erubi" title="erubi">erubi</a>
      or erb (included in Ruby)
    </td>
  </tr>
  <tr>
    <td>File Extensions</td>
    <td>
<tt>.erb</tt>, <tt>.rhtml</tt> or <tt>.erubi</tt> (Erubi only)</td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>erb :index</tt></td>
  </tr>
</table>

<h4 id="builder-templates">Builder Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td>
      <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/jimweirich/builder">https://github.com/jimweirich/builder" title="builder">builder</a>
    </td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td><tt>.builder</tt></td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>builder { |xml| xml.em "hi" }</tt></td>
  </tr>
</table>

<p>It also takes a block for inline templates (see <a href="#inline-templates">example</a>).</p>

<h4 id="nokogiri-templates">Nokogiri Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"http://www.nokogiri.org/" rel="nofollow">http://www.nokogiri.org/" title="nokogiri">nokogiri</a></td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td><tt>.nokogiri</tt></td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>nokogiri { |xml| xml.em "hi" }</tt></td>
  </tr>
</table>

<p>It also takes a block for inline templates (see <a href="#inline-templates">example</a>).</p>

<h4 id="sass-templates">Sass Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/ntkme/sass-embedded-host-ruby">https://github.com/ntkme/sass-embedded-host-ruby" title="sass-embedded">sass-embedded</a></td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td><tt>.sass</tt></td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>sass :stylesheet, :style =&gt; :expanded</tt></td>
  </tr>
</table>

<h4 id="scss-templates">Scss Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/ntkme/sass-embedded-host-ruby">https://github.com/ntkme/sass-embedded-host-ruby" title="sass-embedded">sass-embedded</a></td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td><tt>.scss</tt></td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>scss :stylesheet, :style =&gt; :expanded</tt></td>
  </tr>
</table>

<h4 id="liquid-templates">Liquid Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://shopify.github.io/liquid/" rel="nofollow">https://shopify.github.io/liquid/" title="liquid">liquid</a></td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td><tt>.liquid</tt></td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>liquid :index, :locals =&gt; { :key =&gt; 'value' }</tt></td>
  </tr>
</table>

<p>Since you cannot call Ruby methods (except for <code>yield</code>) from a Liquid
template, you almost always want to pass locals to it.</p>

<h4 id="markdown-templates">Markdown Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td>
      Anyone of:
        <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/davidfstr/rdiscount">https://github.com/davidfstr/rdiscount" title="RDiscount">RDiscount</a>,
        <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/vmg/redcarpet">https://github.com/vmg/redcarpet" title="RedCarpet">RedCarpet</a>,
        <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://kramdown.gettalong.org/" rel="nofollow">https://kramdown.gettalong.org/" title="kramdown">kramdown</a>,
        <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/gjtorikian/commonmarker">https://github.com/gjtorikian/commonmarker" title="commonmarker">commonmarker</a>
        <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/alphabetum/pandoc-ruby">https://github.com/alphabetum/pandoc-ruby" title="pandoc">pandoc</a>
    </td>
  </tr>
  <tr>
    <td>File Extensions</td>
    <td>
<tt>.markdown</tt>, <tt>.mkd</tt> and <tt>.md</tt>
</td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>markdown :index, :layout_engine =&gt; :erb</tt></td>
  </tr>
</table>

<p>It is not possible to call methods from Markdown, nor to pass locals to it.
You therefore will usually use it in combination with another rendering
engine:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">erb</span> <span class="ss">:overview</span><span class="p">,</span> <span class="ss">:locals</span> <span class="o">=&gt;</span> <span class="p">{</span> <span class="ss">:text</span> <span class="o">=&gt;</span> <span class="n">markdown</span><span class="p">(</span><span class="ss">:introduction</span><span class="p">)</span> <span class="p">}</span>
</code></pre></div></div>

<p>Note that you may also call the <code>markdown</code> method from within other
templates:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="o">%</span><span class="n">h1</span> <span class="no">Hello</span> <span class="no">From</span> <span class="no">Haml</span><span class="o">!</span>
<span class="o">%</span><span class="nb">p</span><span class="o">=</span> <span class="n">markdown</span><span class="p">(</span><span class="ss">:greetings</span><span class="p">)</span>
</code></pre></div></div>

<p>Since you cannot call Ruby from Markdown, you cannot use layouts written in
Markdown. However, it is possible to use another rendering engine for the
template than for the layout by passing the <code>:layout_engine</code> option.</p>

<h4 id="rdoc-templates">RDoc Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"http://rdoc.sourceforge.net/" rel="nofollow">http://rdoc.sourceforge.net/" title="RDoc">RDoc</a></td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td><tt>.rdoc</tt></td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>rdoc :README, :layout_engine =&gt; :erb</tt></td>
  </tr>
</table>

<p>It is not possible to call methods from RDoc, nor to pass locals to it. You
therefore will usually use it in combination with another rendering engine:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">erb</span> <span class="ss">:overview</span><span class="p">,</span> <span class="ss">:locals</span> <span class="o">=&gt;</span> <span class="p">{</span> <span class="ss">:text</span> <span class="o">=&gt;</span> <span class="n">rdoc</span><span class="p">(</span><span class="ss">:introduction</span><span class="p">)</span> <span class="p">}</span>
</code></pre></div></div>

<p>Note that you may also call the <code>rdoc</code> method from within other templates:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="o">%</span><span class="n">h1</span> <span class="no">Hello</span> <span class="no">From</span> <span class="no">Haml</span><span class="o">!</span>
<span class="o">%</span><span class="nb">p</span><span class="o">=</span> <span class="n">rdoc</span><span class="p">(</span><span class="ss">:greetings</span><span class="p">)</span>
</code></pre></div></div>

<p>Since you cannot call Ruby from RDoc, you cannot use layouts written in
RDoc. However, it is possible to use another rendering engine for the
template than for the layout by passing the <code>:layout_engine</code> option.</p>

<h4 id="asciidoc-templates">AsciiDoc Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"http://asciidoctor.org/" rel="nofollow">http://asciidoctor.org/" title="Asciidoctor">Asciidoctor</a></td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td>
<tt>.asciidoc</tt>, <tt>.adoc</tt> and <tt>.ad</tt>
</td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>asciidoc :README, :layout_engine =&gt; :erb</tt></td>
  </tr>
</table>

<p>Since you cannot call Ruby methods directly from an AsciiDoc template, you
almost always want to pass locals to it.</p>

<h4 id="markaby-templates">Markaby Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://markaby.github.io/" rel="nofollow">https://markaby.github.io/" title="Markaby">Markaby</a></td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td><tt>.mab</tt></td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>markaby { h1 "Welcome!" }</tt></td>
  </tr>
</table>

<p>It also takes a block for inline templates (see <a href="#inline-templates">example</a>).</p>

<h4 id="rabl-templates">RABL Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/nesquena/rabl">https://github.com/nesquena/rabl" title="Rabl">Rabl</a></td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td><tt>.rabl</tt></td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>rabl :index</tt></td>
  </tr>
</table>

<h4 id="slim-templates">Slim Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://slim-template.github.io/" rel="nofollow">https://slim-template.github.io/" title="Slim Lang">Slim Lang</a></td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td><tt>.slim</tt></td>
  </tr>
  <tr>
    <td>Example</td>
    <td><tt>slim :index</tt></td>
  </tr>
</table>

<h4 id="yajl-templates">Yajl Templates</h4>

<table>
  <tr>
    <td>Dependency</td>
    <td><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/brianmario/yajl-ruby">https://github.com/brianmario/yajl-ruby" title="yajl-ruby">yajl-ruby</a></td>
  </tr>
  <tr>
    <td>File Extension</td>
    <td><tt>.yajl</tt></td>
  </tr>
  <tr>
    <td>Example</td>
    <td>
      <tt>
        yajl :index,
             :locals =&gt; { :key =&gt; 'qux' },
             :callback =&gt; 'present',
             :variable =&gt; 'resource'
      </tt>
    </td>
  </tr>
</table>

<p>The template source is evaluated as a Ruby string, and the
resulting json variable is converted using <code>#to_json</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">json</span> <span class="o">=</span> <span class="p">{</span> <span class="ss">:foo</span> <span class="o">=&gt;</span> <span class="s1">'bar'</span> <span class="p">}</span>
<span class="n">json</span><span class="p">[</span><span class="ss">:baz</span><span class="p">]</span> <span class="o">=</span> <span class="n">key</span>
</code></pre></div></div>

<p>The <code>:callback</code> and <code>:variable</code> options can be used to decorate the rendered
object:</p>

<div class="language-javascript highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">var</span> <span class="nx">resource</span> <span class="o">=</span> <span class="p">{</span><span class="dl">"</span><span class="s2">foo</span><span class="dl">"</span><span class="p">:</span><span class="dl">"</span><span class="s2">bar</span><span class="dl">"</span><span class="p">,</span><span class="dl">"</span><span class="s2">baz</span><span class="dl">"</span><span class="p">:</span><span class="dl">"</span><span class="s2">qux</span><span class="dl">"</span><span class="p">};</span>
<span class="nx">present</span><span class="p">(</span><span class="nx">resource</span><span class="p">);</span>
</code></pre></div></div>

<h3 id="accessing-variables-in-templates">Accessing Variables in Templates</h3>

<p>Templates are evaluated within the same context as route handlers. Instance
variables set in route handlers are directly accessible by templates:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/:id'</span> <span class="k">do</span>
  <span class="vi">@foo</span> <span class="o">=</span> <span class="no">Foo</span><span class="p">.</span><span class="nf">find</span><span class="p">(</span><span class="n">params</span><span class="p">[</span><span class="s1">'id'</span><span class="p">])</span>
  <span class="n">haml</span> <span class="s1">'%h1= @foo.name'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Or, specify an explicit Hash of local variables:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/:id'</span> <span class="k">do</span>
  <span class="n">foo</span> <span class="o">=</span> <span class="no">Foo</span><span class="p">.</span><span class="nf">find</span><span class="p">(</span><span class="n">params</span><span class="p">[</span><span class="s1">'id'</span><span class="p">])</span>
  <span class="n">haml</span> <span class="s1">'%h1= bar.name'</span><span class="p">,</span> <span class="ss">:locals</span> <span class="o">=&gt;</span> <span class="p">{</span> <span class="ss">:bar</span> <span class="o">=&gt;</span> <span class="n">foo</span> <span class="p">}</span>
<span class="k">end</span>
</code></pre></div></div>

<p>This is typically used when rendering templates as partials from within
other templates.</p>

<h3 id="templates-with-yield-and-nested-layouts">Templates with <code>yield</code> and nested layouts</h3>

<p>A layout is usually just a template that calls <code>yield</code>.
Such a template can be used either through the <code>:template</code> option as
described above, or it can be rendered with a block as follows:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">erb</span> <span class="ss">:post</span><span class="p">,</span> <span class="ss">:layout</span> <span class="o">=&gt;</span> <span class="kp">false</span> <span class="k">do</span>
  <span class="n">erb</span> <span class="ss">:index</span>
<span class="k">end</span>
</code></pre></div></div>

<p>This code is mostly equivalent to <code>erb :index, :layout =&gt; :post</code>.</p>

<p>Passing blocks to rendering methods is most useful for creating nested
layouts:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">erb</span> <span class="ss">:main_layout</span><span class="p">,</span> <span class="ss">:layout</span> <span class="o">=&gt;</span> <span class="kp">false</span> <span class="k">do</span>
  <span class="n">erb</span> <span class="ss">:admin_layout</span> <span class="k">do</span>
    <span class="n">erb</span> <span class="ss">:user</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<p>This can also be done in fewer lines of code with:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">erb</span> <span class="ss">:admin_layout</span><span class="p">,</span> <span class="ss">:layout</span> <span class="o">=&gt;</span> <span class="ss">:main_layout</span> <span class="k">do</span>
  <span class="n">erb</span> <span class="ss">:user</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Currently, the following rendering methods accept a block: <code>erb</code>, <code>haml</code>,
<code>liquid</code>, <code>slim </code>. Also, the general <code>render</code> method accepts a block.</p>

<h3 id="inline-templates">Inline Templates</h3>

<p>Templates may be defined at the end of the source file:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'sinatra'</span>

<span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">haml</span> <span class="ss">:index</span>
<span class="k">end</span>

<span class="cp">__END__

@@ layout
%html
  != yield

@@ index
%div.title Hello world.
</span></code></pre></div></div>

<p>NOTE: Inline templates defined in the source file that requires Sinatra are
automatically loaded. Call <code>enable :inline_templates</code> explicitly if you
have inline templates in other source files.</p>

<h3 id="named-templates">Named Templates</h3>

<p>Templates may also be defined using the top-level <code>template</code> method:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">template</span> <span class="ss">:layout</span> <span class="k">do</span>
  <span class="s2">"%html</span><span class="se">\n</span><span class="s2">  =yield</span><span class="se">\n</span><span class="s2">"</span>
<span class="k">end</span>

<span class="n">template</span> <span class="ss">:index</span> <span class="k">do</span>
  <span class="s1">'%div.title Hello World!'</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">haml</span> <span class="ss">:index</span>
<span class="k">end</span>
</code></pre></div></div>

<p>If a template named “layout” exists, it will be used each time a template
is rendered. You can individually disable layouts by passing
<code>:layout =&gt; false</code> or disable them by default via
<code>set :haml, :layout =&gt; false</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">haml</span> <span class="ss">:index</span><span class="p">,</span> <span class="ss">:layout</span> <span class="o">=&gt;</span> <span class="o">!</span><span class="n">request</span><span class="p">.</span><span class="nf">xhr?</span>
<span class="k">end</span>
</code></pre></div></div>

<h3 id="associating-file-extensions">Associating File Extensions</h3>

<p>To associate a file extension with a template engine, use
<code>Tilt.register</code>. For instance, if you like to use the file extension
<code>tt</code> for Haml templates, you can do the following:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="no">Tilt</span><span class="p">.</span><span class="nf">register</span> <span class="no">Tilt</span><span class="p">[</span><span class="ss">:haml</span><span class="p">],</span> <span class="ss">:tt</span>
</code></pre></div></div>

<h3 id="adding-your-own-template-engine">Adding Your Own Template Engine</h3>

<p>First, register your engine with Tilt, then create a rendering method:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="no">Tilt</span><span class="p">.</span><span class="nf">register</span> <span class="no">MyAwesomeTemplateEngine</span><span class="p">,</span> <span class="ss">:myat</span>

<span class="n">helpers</span> <span class="k">do</span>
  <span class="k">def</span> <span class="nf">myat</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">)</span> <span class="n">render</span><span class="p">(</span><span class="ss">:myat</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">)</span> <span class="k">end</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">myat</span> <span class="ss">:index</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Renders <code>./views/index.myat</code>. Learn more about
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/rtomayko/tilt#readme">Tilt</a>.</p">https://github.com/rtomayko/tilt#readme">Tilt</a>.</p>

<h3 id="using-custom-logic-for-template-lookup">Using Custom Logic for Template Lookup</h3>

<p>To implement your own template lookup mechanism you can write your
own <code>#find_template</code> method:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">configure</span> <span class="k">do</span>
  <span class="n">set</span> <span class="ss">:views</span><span class="p">,</span> <span class="p">[</span> <span class="s1">'./views/a'</span><span class="p">,</span> <span class="s1">'./views/b'</span> <span class="p">]</span>
<span class="k">end</span>

<span class="k">def</span> <span class="nf">find_template</span><span class="p">(</span><span class="n">views</span><span class="p">,</span> <span class="nb">name</span><span class="p">,</span> <span class="n">engine</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">block</span><span class="p">)</span>
  <span class="no">Array</span><span class="p">(</span><span class="n">views</span><span class="p">).</span><span class="nf">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">v</span><span class="o">|</span>
    <span class="k">super</span><span class="p">(</span><span class="n">v</span><span class="p">,</span> <span class="nb">name</span><span class="p">,</span> <span class="n">engine</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">block</span><span class="p">)</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<h2 id="filters">Filters</h2>

<p>Before filters are evaluated before each request within the same context
as the routes will be and can modify the request and response. Instance
variables set in filters are accessible by routes and templates:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">before</span> <span class="k">do</span>
  <span class="vi">@note</span> <span class="o">=</span> <span class="s1">'Hi!'</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">path_info</span> <span class="o">=</span> <span class="s1">'/foo/bar/baz'</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/foo/*'</span> <span class="k">do</span>
  <span class="vi">@note</span> <span class="c1">#=&gt; 'Hi!'</span>
  <span class="n">params</span><span class="p">[</span><span class="s1">'splat'</span><span class="p">]</span> <span class="c1">#=&gt; 'bar/baz'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>After filters are evaluated after each request within the same context
as the routes will be and can also modify the request and response.
Instance variables set in before filters and routes are accessible by
after filters:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">after</span> <span class="k">do</span>
  <span class="nb">puts</span> <span class="n">response</span><span class="p">.</span><span class="nf">status</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Note: Unless you use the <code>body</code> method rather than just returning a
String from the routes, the body will not yet be available in the after
filter, since it is generated later on.</p>

<p>Filters optionally take a pattern, causing them to be evaluated only if the
request path matches that pattern:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">before</span> <span class="s1">'/protected/*'</span> <span class="k">do</span>
  <span class="n">authenticate!</span>
<span class="k">end</span>

<span class="n">after</span> <span class="s1">'/create/:slug'</span> <span class="k">do</span> <span class="o">|</span><span class="n">slug</span><span class="o">|</span>
  <span class="n">session</span><span class="p">[</span><span class="ss">:last_slug</span><span class="p">]</span> <span class="o">=</span> <span class="n">slug</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Like routes, filters also take conditions:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">before</span> <span class="ss">:agent</span> <span class="o">=&gt;</span> <span class="sr">/Songbird/</span> <span class="k">do</span>
  <span class="c1"># ...</span>
<span class="k">end</span>

<span class="n">after</span> <span class="s1">'/blog/*'</span><span class="p">,</span> <span class="ss">:host_name</span> <span class="o">=&gt;</span> <span class="s1">'example.com'</span> <span class="k">do</span>
  <span class="c1"># ...</span>
<span class="k">end</span>
</code></pre></div></div>

<h2 id="helpers">Helpers</h2>

<p>Use the top-level <code>helpers</code> method to define helper methods for use in
route handlers and templates:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">helpers</span> <span class="k">do</span>
  <span class="k">def</span> <span class="nf">bar</span><span class="p">(</span><span class="nb">name</span><span class="p">)</span>
    <span class="s2">"</span><span class="si">#{</span><span class="nb">name</span><span class="si">}</span><span class="s2">bar"</span>
  <span class="k">end</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/:name'</span> <span class="k">do</span>
  <span class="n">bar</span><span class="p">(</span><span class="n">params</span><span class="p">[</span><span class="s1">'name'</span><span class="p">])</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Alternatively, helper methods can be separately defined in a module:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">module</span> <span class="nn">FooUtils</span>
  <span class="k">def</span> <span class="nf">foo</span><span class="p">(</span><span class="nb">name</span><span class="p">)</span> <span class="s2">"</span><span class="si">#{</span><span class="nb">name</span><span class="si">}</span><span class="s2">foo"</span> <span class="k">end</span>
<span class="k">end</span>

<span class="k">module</span> <span class="nn">BarUtils</span>
  <span class="k">def</span> <span class="nf">bar</span><span class="p">(</span><span class="nb">name</span><span class="p">)</span> <span class="s2">"</span><span class="si">#{</span><span class="nb">name</span><span class="si">}</span><span class="s2">bar"</span> <span class="k">end</span>
<span class="k">end</span>

<span class="n">helpers</span> <span class="no">FooUtils</span><span class="p">,</span> <span class="no">BarUtils</span>
</code></pre></div></div>

<p>The effect is the same as including the modules in the application class.</p>

<h3 id="using-sessions">Using Sessions</h3>

<p>A session is used to keep state during requests. If activated, you have one
session hash per user session:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">enable</span> <span class="ss">:sessions</span>

<span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="s2">"value = "</span> <span class="o">&lt;&lt;</span> <span class="n">session</span><span class="p">[</span><span class="ss">:value</span><span class="p">].</span><span class="nf">inspect</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/:value'</span> <span class="k">do</span>
  <span class="n">session</span><span class="p">[</span><span class="s1">'value'</span><span class="p">]</span> <span class="o">=</span> <span class="n">params</span><span class="p">[</span><span class="s1">'value'</span><span class="p">]</span>
<span class="k">end</span>
</code></pre></div></div>

<h4 id="session-secret-security">Session Secret Security</h4>

<p>To improve security, the session data in the cookie is signed with a session
secret using <code>HMAC-SHA1</code>. This session secret should optimally be a
cryptographically secure random value of an appropriate length which for
<code>HMAC-SHA1</code> is greater than or equal to 64 bytes (512 bits, 128 hex
characters). You would be advised not to use a secret that is less than 32
bytes of randomness (256 bits, 64 hex characters). It is therefore <strong>very
important</strong> that you don’t just make the secret up, but instead use a secure
random number generator to create it. Humans are extremely bad at generating
random values.</p>

<p>By default, a 32 byte secure random session secret is generated for you by
Sinatra, but it will change with every restart of your application. If you
have multiple instances of your application, and you let Sinatra generate the
key, each instance would then have a different session key which is probably
not what you want.</p>

<p>For better security and usability it’s
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://12factor.net/config">recommended</a" rel="nofollow">https://12factor.net/config">recommended</a> that you generate a secure random
secret and store it in an environment variable on each host running your
application so that all of your application instances will share the same
secret. You should periodically rotate this session secret to a new value.
Here are some examples of how you might create a 64-byte secret and set it:</p>

<p><strong>Session Secret Generation</strong></p>

<pre><code class="language-text">$ ruby -e "require 'securerandom'; puts SecureRandom.hex(64)"
99ae8af...snip...ec0f262ac
</code></pre>

<p><strong>Session Secret Environment Variable</strong></p>

<p>Set a <code>SESSION_SECRET</code> environment variable for Sinatra to the value you
generated. Make this value persistent across reboots of your host. Since the
method for doing this will vary across systems this is for illustrative
purposes only:</p>

<div class="language-bash highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c"># echo "export SESSION_SECRET=99ae8af...snip...ec0f262ac" &gt;&gt; ~/.bashrc</span>
</code></pre></div></div>

<p><strong>Session Secret App Config</strong></p>

<p>Set up your app config to fail-safe to a secure random secret
if the <code>SESSION_SECRET</code> environment variable is not available:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'securerandom'</span>
<span class="n">set</span> <span class="ss">:session_secret</span><span class="p">,</span> <span class="no">ENV</span><span class="p">.</span><span class="nf">fetch</span><span class="p">(</span><span class="s1">'SESSION_SECRET'</span><span class="p">)</span> <span class="p">{</span> <span class="no">SecureRandom</span><span class="p">.</span><span class="nf">hex</span><span class="p">(</span><span class="mi">64</span><span class="p">)</span> <span class="p">}</span>
</code></pre></div></div>

<h4 id="session-config">Session Config</h4>

<p>If you want to configure it further, you may also store a hash with options
in the <code>sessions</code> setting:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:sessions</span><span class="p">,</span> <span class="ss">:domain</span> <span class="o">=&gt;</span> <span class="s1">'foo.com'</span>
</code></pre></div></div>

<p>To share your session across other apps on subdomains of foo.com, prefix the
domain with a <em>.</em> like this instead:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:sessions</span><span class="p">,</span> <span class="ss">:domain</span> <span class="o">=&gt;</span> <span class="s1">'.foo.com'</span>
</code></pre></div></div>

<h4 id="choosing-your-own-session-middleware">Choosing Your Own Session Middleware</h4>

<p>Note that <code>enable :sessions</code> actually stores all data in a cookie. This
might not always be what you want (storing lots of data will increase your
traffic, for instance). You can use any Rack session middleware in order to
do so, one of the following methods can be used:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">enable</span> <span class="ss">:sessions</span>
<span class="n">set</span> <span class="ss">:session_store</span><span class="p">,</span> <span class="no">Rack</span><span class="o">::</span><span class="no">Session</span><span class="o">::</span><span class="no">Pool</span>
</code></pre></div></div>

<p>Or to set up sessions with a hash of options:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:sessions</span><span class="p">,</span> <span class="ss">:expire_after</span> <span class="o">=&gt;</span> <span class="mi">2592000</span>
<span class="n">set</span> <span class="ss">:session_store</span><span class="p">,</span> <span class="no">Rack</span><span class="o">::</span><span class="no">Session</span><span class="o">::</span><span class="no">Pool</span>
</code></pre></div></div>

<p>Another option is to <strong>not</strong> call <code>enable :sessions</code>, but instead pull in
your middleware of choice as you would any other middleware.</p>

<p>It is important to note that when using this method, session based
protection <strong>will not be enabled by default</strong>.</p>

<p>The Rack middleware to do that will also need to be added:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">use</span> <span class="no">Rack</span><span class="o">::</span><span class="no">Session</span><span class="o">::</span><span class="no">Pool</span><span class="p">,</span> <span class="ss">:expire_after</span> <span class="o">=&gt;</span> <span class="mi">2592000</span>
<span class="n">use</span> <span class="no">Rack</span><span class="o">::</span><span class="no">Protection</span><span class="o">::</span><span class="no">RemoteToken</span>
<span class="n">use</span> <span class="no">Rack</span><span class="o">::</span><span class="no">Protection</span><span class="o">::</span><span class="no">SessionHijacking</span>
</code></pre></div></div>

<p>See ‘<a href="#configuring-attack-protection">Configuring attack protection</a>’ for more information.</p>

<h3 id="halting">Halting</h3>

<p>To immediately stop a request within a filter or route use:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">halt</span>
</code></pre></div></div>

<p>You can also specify the status when halting:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">halt</span> <span class="mi">410</span>
</code></pre></div></div>

<p>Or the body:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">halt</span> <span class="s1">'this will be the body'</span>
</code></pre></div></div>

<p>Or both:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">halt</span> <span class="mi">401</span><span class="p">,</span> <span class="s1">'go away!'</span>
</code></pre></div></div>

<p>With headers:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">halt</span> <span class="mi">402</span><span class="p">,</span> <span class="p">{</span><span class="s1">'Content-Type'</span> <span class="o">=&gt;</span> <span class="s1">'text/plain'</span><span class="p">},</span> <span class="s1">'revenge'</span>
</code></pre></div></div>

<p>It is of course possible to combine a template with <code>halt</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">halt</span> <span class="n">erb</span><span class="p">(</span><span class="ss">:error</span><span class="p">)</span>
</code></pre></div></div>

<h3 id="passing">Passing</h3>

<p>A route can punt processing to the next matching route using <code>pass</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/guess/:who'</span> <span class="k">do</span>
  <span class="n">pass</span> <span class="k">unless</span> <span class="n">params</span><span class="p">[</span><span class="s1">'who'</span><span class="p">]</span> <span class="o">==</span> <span class="s1">'Frank'</span>
  <span class="s1">'You got me!'</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/guess/*'</span> <span class="k">do</span>
  <span class="s1">'You missed!'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>The route block is immediately exited and control continues with the next
matching route. If no matching route is found, a 404 is returned.</p>

<h3 id="triggering-another-route">Triggering Another Route</h3>

<p>Sometimes <code>pass</code> is not what you want, instead, you would like to get the
result of calling another route. Simply use <code>call</code> to achieve this:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/foo'</span> <span class="k">do</span>
  <span class="n">status</span><span class="p">,</span> <span class="n">headers</span><span class="p">,</span> <span class="n">body</span> <span class="o">=</span> <span class="n">call</span> <span class="n">env</span><span class="p">.</span><span class="nf">merge</span><span class="p">(</span><span class="s2">"PATH_INFO"</span> <span class="o">=&gt;</span> <span class="s1">'/bar'</span><span class="p">)</span>
  <span class="p">[</span><span class="n">status</span><span class="p">,</span> <span class="n">headers</span><span class="p">,</span> <span class="n">body</span><span class="p">.</span><span class="nf">map</span><span class="p">(</span><span class="o">&amp;</span><span class="ss">:upcase</span><span class="p">)]</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/bar'</span> <span class="k">do</span>
  <span class="s2">"bar"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Note that in the example above, you would ease testing and increase
performance by simply moving <code>"bar"</code> into a helper used by both <code>/foo</code> and
<code>/bar</code>.</p>

<p>If you want the request to be sent to the same application instance rather
than a duplicate, use <code>call!</code> instead of <code>call</code>.</p>

<p>Check out the Rack specification if you want to learn more about <code>call</code>.</p>

<h3 id="setting-body-status-code-and-headers">Setting Body, Status Code, and Headers</h3>

<p>It is possible and recommended to set the status code and response body with
the return value of the route block. However, in some scenarios, you might
want to set the body at an arbitrary point in the execution flow. You can do
so with the <code>body</code> helper method. If you do so, you can use that method from
thereon to access the body:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/foo'</span> <span class="k">do</span>
  <span class="n">body</span> <span class="s2">"bar"</span>
<span class="k">end</span>

<span class="n">after</span> <span class="k">do</span>
  <span class="nb">puts</span> <span class="n">body</span>
<span class="k">end</span>
</code></pre></div></div>

<p>It is also possible to pass a block to <code>body</code>, which will be executed by the
Rack handler (this can be used to implement streaming, <a href="#return-values">see “Return Values”</a>).</p>

<p>Similar to the body, you can also set the status code and headers:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/foo'</span> <span class="k">do</span>
  <span class="n">status</span> <span class="mi">418</span>
  <span class="n">headers</span> <span class="p">\</span>
    <span class="s2">"Allow"</span>   <span class="o">=&gt;</span> <span class="s2">"BREW, POST, GET, PROPFIND, WHEN"</span><span class="p">,</span>
    <span class="s2">"Refresh"</span> <span class="o">=&gt;</span> <span class="s2">"Refresh: 20; https://ietf.org/rfc/rfc2324.txt"</span>
  <span class="n">body</span> <span class="s2">"I'm a teapot!"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Like <code>body</code>, <code>headers</code> and <code>status</code> with no arguments can be used to access
their current values.</p>

<h3 id="streaming-responses">Streaming Responses</h3>

<p>Sometimes you want to start sending out data while still generating parts of
the response body. In extreme examples, you want to keep sending data until
the client closes the connection. You can use the <code>stream</code> helper to avoid
creating your own wrapper:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">stream</span> <span class="k">do</span> <span class="o">|</span><span class="n">out</span><span class="o">|</span>
    <span class="n">out</span> <span class="o">&lt;&lt;</span> <span class="s2">"It's gonna be legen -</span><span class="se">\n</span><span class="s2">"</span>
    <span class="nb">sleep</span> <span class="mf">0.5</span>
    <span class="n">out</span> <span class="o">&lt;&lt;</span> <span class="s2">" (wait for it) </span><span class="se">\n</span><span class="s2">"</span>
    <span class="nb">sleep</span> <span class="mi">1</span>
    <span class="n">out</span> <span class="o">&lt;&lt;</span> <span class="s2">"- dary!</span><span class="se">\n</span><span class="s2">"</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<p>This allows you to implement streaming APIs,
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://w3c.github.io/eventsource/">Server" rel="nofollow">https://w3c.github.io/eventsource/">Server Sent Events</a>, and can be used as
the basis for <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://en.wikipedia.org/wiki/WebSocket">WebSockets</a" rel="nofollow">https://en.wikipedia.org/wiki/WebSocket">WebSockets</a>. It can
also be used to increase throughput if some but not all content depends on a
slow resource.</p>

<p>Note that the streaming behavior, especially the number of concurrent
requests, highly depends on the webserver used to serve the application.
Some servers might not even support streaming at all. If the server does not
support streaming, the body will be sent all at once after the block passed
to <code>stream</code> finishes executing. Streaming does not work at all with Shotgun.</p>

<p>If the optional parameter is set to <code>keep_open</code>, it will not call <code>close</code> on
the stream object, allowing you to close it at any later point in the
execution flow.</p>

<p>You can have a look at the <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/sinatra/sinatra/blob/main/examples/chat.rb">chat">https://github.com/sinatra/sinatra/blob/main/examples/chat.rb">chat example</a></p>

<p>It’s also possible for the client to close the connection when trying to
write to the socket. Because of this, it’s recommended to check
<code>out.closed?</code> before trying to write.</p>

<h3 id="logging">Logging</h3>

<p>In the request scope, the <code>logger</code> helper exposes a <code>Logger</code> instance:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">logger</span><span class="p">.</span><span class="nf">info</span> <span class="s2">"loading data"</span>
  <span class="c1"># ...</span>
<span class="k">end</span>
</code></pre></div></div>

<p>This logger will automatically take your Rack handler’s logging settings into
account. If logging is disabled, this method will return a dummy object, so
you do not have to worry about it in your routes and filters.</p>

<p>Note that logging is only enabled for <code>Sinatra::Application</code> by default, so
if you inherit from <code>Sinatra::Base</code>, you probably want to enable it yourself:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="nc">MyApp</span> <span class="o">&lt;</span> <span class="no">Sinatra</span><span class="o">::</span><span class="no">Base</span>
  <span class="n">configure</span> <span class="ss">:production</span><span class="p">,</span> <span class="ss">:development</span> <span class="k">do</span>
    <span class="n">enable</span> <span class="ss">:logging</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<p>To avoid any logging middleware to be set up, set the <code>logging</code> option to
<code>nil</code>. However, keep in mind that <code>logger</code> will in that case return <code>nil</code>. A
common use case is when you want to set your own logger. Sinatra will use
whatever it will find in <code>env['rack.logger']</code>.</p>

<h3 id="mime-types">Mime Types</h3>

<p>When using <code>send_file</code> or static files you may have mime types Sinatra
doesn’t understand. Use <code>mime_type</code> to register them by file extension:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">configure</span> <span class="k">do</span>
  <span class="n">mime_type</span> <span class="ss">:foo</span><span class="p">,</span> <span class="s1">'text/foo'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>You can also use it with the <code>content_type</code> helper:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">content_type</span> <span class="ss">:foo</span>
  <span class="s2">"foo foo foo"</span>
<span class="k">end</span>
</code></pre></div></div>

<h3 id="generating-urls">Generating URLs</h3>

<p>For generating URLs you should use the <code>url</code> helper method, for instance, in
Haml:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="o">%</span><span class="n">a</span><span class="p">{</span><span class="ss">:href</span> <span class="o">=&gt;</span> <span class="n">url</span><span class="p">(</span><span class="s1">'/foo'</span><span class="p">)}</span> <span class="n">foo</span>
</code></pre></div></div>

<p>It takes reverse proxies and Rack routers into account - if present.</p>

<p>This method is also aliased to <code>to</code> (see <a href="#browser-redirect">below</a> for an example).</p>

<h3 id="browser-redirect">Browser Redirect</h3>

<p>You can trigger a browser redirect with the <code>redirect</code> helper method:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/foo'</span> <span class="k">do</span>
  <span class="n">redirect</span> <span class="n">to</span><span class="p">(</span><span class="s1">'/bar'</span><span class="p">)</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Any additional parameters are handled like arguments passed to <code>halt</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">redirect</span> <span class="n">to</span><span class="p">(</span><span class="s1">'/bar'</span><span class="p">),</span> <span class="mi">303</span>
<span class="n">redirect</span> <span class="s1">'http://www.google.com/'</span><span class="p">,</span> <span class="s1">'wrong place, buddy'</span>
</code></pre></div></div>

<p>You can also easily redirect back to the page the user came from with
<code>redirect back</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/foo'</span> <span class="k">do</span>
  <span class="s2">"&lt;a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fbar"&gt;do something&lt;/a&gt;"</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/bar'</span> <span class="k">do</span>
  <span class="n">do_something</span>
  <span class="n">redirect</span> <span class="n">back</span>
<span class="k">end</span>
</code></pre></div></div>

<p>To pass arguments with a redirect, either add them to the query:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">redirect</span> <span class="n">to</span><span class="p">(</span><span class="s1">'/bar?sum=42'</span><span class="p">)</span>
</code></pre></div></div>

<p>Or use a session:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">enable</span> <span class="ss">:sessions</span>

<span class="n">get</span> <span class="s1">'/foo'</span> <span class="k">do</span>
  <span class="n">session</span><span class="p">[</span><span class="ss">:secret</span><span class="p">]</span> <span class="o">=</span> <span class="s1">'foo'</span>
  <span class="n">redirect</span> <span class="n">to</span><span class="p">(</span><span class="s1">'/bar'</span><span class="p">)</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/bar'</span> <span class="k">do</span>
  <span class="n">session</span><span class="p">[</span><span class="ss">:secret</span><span class="p">]</span>
<span class="k">end</span>
</code></pre></div></div>

<h3 id="cache-control">Cache Control</h3>

<p>Setting your headers correctly is the foundation for proper HTTP caching.</p>

<p>You can easily set the Cache-Control header like this:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">cache_control</span> <span class="ss">:public</span>
  <span class="s2">"cache it!"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Pro tip: Set up caching in a before filter:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">before</span> <span class="k">do</span>
  <span class="n">cache_control</span> <span class="ss">:public</span><span class="p">,</span> <span class="ss">:must_revalidate</span><span class="p">,</span> <span class="ss">:max_age</span> <span class="o">=&gt;</span> <span class="mi">60</span>
<span class="k">end</span>
</code></pre></div></div>

<p>If you are using the <code>expires</code> helper to set the corresponding header,
<code>Cache-Control</code> will be set automatically for you:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">before</span> <span class="k">do</span>
  <span class="n">expires</span> <span class="mi">500</span><span class="p">,</span> <span class="ss">:public</span><span class="p">,</span> <span class="ss">:must_revalidate</span>
<span class="k">end</span>
</code></pre></div></div>

<p>To properly use caches, you should consider using <code>etag</code> or <code>last_modified</code>.
It is recommended to call those helpers <em>before</em> doing any heavy lifting, as
they will immediately flush a response if the client already has the current
version in its cache:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s2">"/article/:id"</span> <span class="k">do</span>
  <span class="vi">@article</span> <span class="o">=</span> <span class="no">Article</span><span class="p">.</span><span class="nf">find</span> <span class="n">params</span><span class="p">[</span><span class="s1">'id'</span><span class="p">]</span>
  <span class="n">last_modified</span> <span class="vi">@article</span><span class="p">.</span><span class="nf">updated_at</span>
  <span class="n">etag</span> <span class="vi">@article</span><span class="p">.</span><span class="nf">sha1</span>
  <span class="n">erb</span> <span class="ss">:article</span>
<span class="k">end</span>
</code></pre></div></div>

<p>It is also possible to use a
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://en.wikipedia.org/wiki/HTTP_ETag#Strong_and_weak_validation">weak" rel="nofollow">https://en.wikipedia.org/wiki/HTTP_ETag#Strong_and_weak_validation">weak ETag</a>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">etag</span> <span class="vi">@article</span><span class="p">.</span><span class="nf">sha1</span><span class="p">,</span> <span class="ss">:weak</span>
</code></pre></div></div>

<p>These helpers will not do any caching for you, but rather feed the necessary
information to your cache. If you are looking for a quick
reverse-proxy caching solution, try
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/rtomayko/rack-cache#readme">rack-cache</a>:</p">https://github.com/rtomayko/rack-cache#readme">rack-cache</a>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s2">"rack/cache"</span>
<span class="nb">require</span> <span class="s2">"sinatra"</span>

<span class="n">use</span> <span class="no">Rack</span><span class="o">::</span><span class="no">Cache</span>

<span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">cache_control</span> <span class="ss">:public</span><span class="p">,</span> <span class="ss">:max_age</span> <span class="o">=&gt;</span> <span class="mi">36000</span>
  <span class="nb">sleep</span> <span class="mi">5</span>
  <span class="s2">"hello"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Use the <code>:static_cache_control</code> setting (see <a href="#cache-control">below</a>) to add
<code>Cache-Control</code> header info to static files.</p>

<p>According to RFC 2616, your application should behave differently if the
If-Match or If-None-Match header is set to <code>*</code>, depending on whether the
resource requested is already in existence. Sinatra assumes resources for
safe (like get) and idempotent (like put) requests are already in existence,
whereas other resources (for instance post requests) are treated as new
resources. You can change this behavior by passing in a <code>:new_resource</code>
option:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/create'</span> <span class="k">do</span>
  <span class="n">etag</span> <span class="s1">''</span><span class="p">,</span> <span class="ss">:new_resource</span> <span class="o">=&gt;</span> <span class="kp">true</span>
  <span class="no">Article</span><span class="p">.</span><span class="nf">create</span>
  <span class="n">erb</span> <span class="ss">:new_article</span>
<span class="k">end</span>
</code></pre></div></div>

<p>If you still want to use a weak ETag, pass in a <code>:kind</code> option:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">etag</span> <span class="s1">''</span><span class="p">,</span> <span class="ss">:new_resource</span> <span class="o">=&gt;</span> <span class="kp">true</span><span class="p">,</span> <span class="ss">:kind</span> <span class="o">=&gt;</span> <span class="ss">:weak</span>
</code></pre></div></div>

<h3 id="sending-files">Sending Files</h3>

<p>To return the contents of a file as the response, you can use the <code>send_file</code>
helper method:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">send_file</span> <span class="s1">'foo.png'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>It also takes options:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">send_file</span> <span class="s1">'foo.png'</span><span class="p">,</span> <span class="ss">:type</span> <span class="o">=&gt;</span> <span class="ss">:jpg</span>
</code></pre></div></div>

<p>The options are:</p>

<dl>
  <dt>filename</dt>
    <dd>File name to be used in the response,
    defaults to the real file name.</dd>
  <dt>last_modified</dt>
    <dd>Value for Last-Modified header, defaults to the file's mtime.</dd>

  <dt>type</dt>
    <dd>Value for Content-Type header, guessed from the file extension if
    missing.</dd>

  <dt>disposition</dt>
    <dd>
      Value for Content-Disposition header, possible values: <tt>nil</tt>
      (default), <tt>:attachment</tt> and <tt>:inline</tt>
    </dd>

  <dt>length</dt>
    <dd>Value for Content-Length header, defaults to file size.</dd>

  <dt>status</dt>
    <dd>
      Status code to be sent. Useful when sending a static file as an error
      page. If supported by the Rack handler, other means than streaming
      from the Ruby process will be used. If you use this helper method,
      Sinatra will automatically handle range requests.
    </dd>
</dl>

<h3 id="accessing-the-request-object">Accessing the Request Object</h3>

<p>The incoming request object can be accessed from request level (filter,
routes, error handlers) through the <code>request</code> method:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># app running on http://example.com/example</span>
<span class="n">get</span> <span class="s1">'/foo'</span> <span class="k">do</span>
  <span class="n">t</span> <span class="o">=</span> <span class="sx">%w[text/css text/html application/javascript]</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">accept</span>              <span class="c1"># ['text/html', '*/*']</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">accept?</span> <span class="s1">'text/xml'</span>  <span class="c1"># true</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">preferred_type</span><span class="p">(</span><span class="n">t</span><span class="p">)</span>   <span class="c1"># 'text/html'</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">body</span>                <span class="c1"># request body sent by the client (see below)</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">scheme</span>              <span class="c1"># "http"</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">script_name</span>         <span class="c1"># "/example"</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">path_info</span>           <span class="c1"># "/foo"</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">port</span>                <span class="c1"># 80</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">request_method</span>      <span class="c1"># "GET"</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">query_string</span>        <span class="c1"># ""</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">content_length</span>      <span class="c1"># length of request.body</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">media_type</span>          <span class="c1"># media type of request.body</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">host</span>                <span class="c1"># "example.com"</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">get?</span>                <span class="c1"># true (similar methods for other verbs)</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">form_data?</span>          <span class="c1"># false</span>
  <span class="n">request</span><span class="p">[</span><span class="s2">"some_param"</span><span class="p">]</span>       <span class="c1"># value of some_param parameter. [] is a shortcut to the params hash.</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">referrer</span>            <span class="c1"># the referrer of the client or '/'</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">user_agent</span>          <span class="c1"># user agent (used by :agent condition)</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">cookies</span>             <span class="c1"># hash of browser cookies</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">xhr?</span>                <span class="c1"># is this an ajax request?</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">url</span>                 <span class="c1"># "http://example.com/example/foo"</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">path</span>                <span class="c1"># "/example/foo"</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">ip</span>                  <span class="c1"># client IP address</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">secure?</span>             <span class="c1"># false (would be true over ssl)</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">forwarded?</span>          <span class="c1"># true (if running behind a reverse proxy)</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">env</span>                 <span class="c1"># raw env hash handed in by Rack</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Some options, like <code>script_name</code> or <code>path_info</code>, can also be written:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">before</span> <span class="p">{</span> <span class="n">request</span><span class="p">.</span><span class="nf">path_info</span> <span class="o">=</span> <span class="s2">"/"</span> <span class="p">}</span>

<span class="n">get</span> <span class="s2">"/"</span> <span class="k">do</span>
  <span class="s2">"all requests end up here"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>The <code>request.body</code> is an IO or StringIO object:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">post</span> <span class="s2">"/api"</span> <span class="k">do</span>
  <span class="n">request</span><span class="p">.</span><span class="nf">body</span><span class="p">.</span><span class="nf">rewind</span>  <span class="c1"># in case someone already read it</span>
  <span class="n">data</span> <span class="o">=</span> <span class="no">JSON</span><span class="p">.</span><span class="nf">parse</span> <span class="n">request</span><span class="p">.</span><span class="nf">body</span><span class="p">.</span><span class="nf">read</span>
  <span class="s2">"Hello </span><span class="si">#{</span><span class="n">data</span><span class="p">[</span><span class="s1">'name'</span><span class="p">]</span><span class="si">}</span><span class="s2">!"</span>
<span class="k">end</span>
</code></pre></div></div>

<h3 id="attachments">Attachments</h3>

<p>You can use the <code>attachment</code> helper to tell the browser the response should
be stored on disk rather than displayed in the browser:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">attachment</span>
  <span class="s2">"store it!"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>You can also pass it a file name:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">attachment</span> <span class="s2">"info.txt"</span>
  <span class="s2">"store it!"</span>
<span class="k">end</span>
</code></pre></div></div>

<h3 id="dealing-with-date-and-time">Dealing with Date and Time</h3>

<p>Sinatra offers a <code>time_for</code> helper method that generates a Time object from
the given value. It is also able to convert <code>DateTime</code>, <code>Date</code> and similar
classes:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">pass</span> <span class="k">if</span> <span class="no">Time</span><span class="p">.</span><span class="nf">now</span> <span class="o">&gt;</span> <span class="n">time_for</span><span class="p">(</span><span class="s1">'Dec 23, 2016'</span><span class="p">)</span>
  <span class="s2">"still time"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>This method is used internally by <code>expires</code>, <code>last_modified</code> and akin. You
can therefore easily extend the behavior of those methods by overriding
<code>time_for</code> in your application:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">helpers</span> <span class="k">do</span>
  <span class="k">def</span> <span class="nf">time_for</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>
    <span class="k">case</span> <span class="n">value</span>
    <span class="k">when</span> <span class="ss">:yesterday</span> <span class="k">then</span> <span class="no">Time</span><span class="p">.</span><span class="nf">now</span> <span class="o">-</span> <span class="mi">24</span><span class="o">*</span><span class="mi">60</span><span class="o">*</span><span class="mi">60</span>
    <span class="k">when</span> <span class="ss">:tomorrow</span>  <span class="k">then</span> <span class="no">Time</span><span class="p">.</span><span class="nf">now</span> <span class="o">+</span> <span class="mi">24</span><span class="o">*</span><span class="mi">60</span><span class="o">*</span><span class="mi">60</span>
    <span class="k">else</span> <span class="k">super</span>
    <span class="k">end</span>
  <span class="k">end</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">last_modified</span> <span class="ss">:yesterday</span>
  <span class="n">expires</span> <span class="ss">:tomorrow</span>
  <span class="s2">"hello"</span>
<span class="k">end</span>
</code></pre></div></div>

<h3 id="looking-up-template-files">Looking Up Template Files</h3>

<p>The <code>find_template</code> helper is used to find template files for rendering:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">find_template</span> <span class="n">settings</span><span class="p">.</span><span class="nf">views</span><span class="p">,</span> <span class="s1">'foo'</span><span class="p">,</span> <span class="no">Tilt</span><span class="p">[</span><span class="ss">:haml</span><span class="p">]</span> <span class="k">do</span> <span class="o">|</span><span class="n">file</span><span class="o">|</span>
  <span class="nb">puts</span> <span class="s2">"could be </span><span class="si">#{</span><span class="n">file</span><span class="si">}</span><span class="s2">"</span>
<span class="k">end</span>
</code></pre></div></div>

<p>This is not really useful. But it is useful that you can actually override
this method to hook in your own lookup mechanism. For instance, if you want
to be able to use more than one view directory:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:views</span><span class="p">,</span> <span class="p">[</span><span class="s1">'views'</span><span class="p">,</span> <span class="s1">'templates'</span><span class="p">]</span>

<span class="n">helpers</span> <span class="k">do</span>
  <span class="k">def</span> <span class="nf">find_template</span><span class="p">(</span><span class="n">views</span><span class="p">,</span> <span class="nb">name</span><span class="p">,</span> <span class="n">engine</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">block</span><span class="p">)</span>
    <span class="no">Array</span><span class="p">(</span><span class="n">views</span><span class="p">).</span><span class="nf">each</span> <span class="p">{</span> <span class="o">|</span><span class="n">v</span><span class="o">|</span> <span class="k">super</span><span class="p">(</span><span class="n">v</span><span class="p">,</span> <span class="nb">name</span><span class="p">,</span> <span class="n">engine</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">block</span><span class="p">)</span> <span class="p">}</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Another example would be using different directories for different engines:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:views</span><span class="p">,</span> <span class="ss">:haml</span> <span class="o">=&gt;</span> <span class="s1">'templates'</span><span class="p">,</span> <span class="ss">:default</span> <span class="o">=&gt;</span> <span class="s1">'views'</span>

<span class="n">helpers</span> <span class="k">do</span>
  <span class="k">def</span> <span class="nf">find_template</span><span class="p">(</span><span class="n">views</span><span class="p">,</span> <span class="nb">name</span><span class="p">,</span> <span class="n">engine</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">block</span><span class="p">)</span>
    <span class="n">_</span><span class="p">,</span> <span class="n">folder</span> <span class="o">=</span> <span class="n">views</span><span class="p">.</span><span class="nf">detect</span> <span class="p">{</span> <span class="o">|</span><span class="n">k</span><span class="p">,</span><span class="n">v</span><span class="o">|</span> <span class="n">engine</span> <span class="o">==</span> <span class="no">Tilt</span><span class="p">[</span><span class="n">k</span><span class="p">]</span> <span class="p">}</span>
    <span class="n">folder</span> <span class="o">||=</span> <span class="n">views</span><span class="p">[</span><span class="ss">:default</span><span class="p">]</span>
    <span class="k">super</span><span class="p">(</span><span class="n">folder</span><span class="p">,</span> <span class="nb">name</span><span class="p">,</span> <span class="n">engine</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">block</span><span class="p">)</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<p>You can also easily wrap this up in an extension and share it with others!</p>

<p>Note that <code>find_template</code> does not check if the file really exists but
rather calls the given block for all possible paths. This is not a
performance issue, since <code>render</code> will use <code>break</code> as soon as a file is
found. Also, template locations (and content) will be cached if you are not
running in development mode. You should keep that in mind if you write a
really crazy method.</p>

<h2 id="configuration">Configuration</h2>

<p>Run once, at startup, in any environment:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">configure</span> <span class="k">do</span>
  <span class="c1"># setting one option</span>
  <span class="n">set</span> <span class="ss">:option</span><span class="p">,</span> <span class="s1">'value'</span>

  <span class="c1"># setting multiple options</span>
  <span class="n">set</span> <span class="ss">:a</span> <span class="o">=&gt;</span> <span class="mi">1</span><span class="p">,</span> <span class="ss">:b</span> <span class="o">=&gt;</span> <span class="mi">2</span>

  <span class="c1"># same as `set :option, true`</span>
  <span class="n">enable</span> <span class="ss">:option</span>

  <span class="c1"># same as `set :option, false`</span>
  <span class="n">disable</span> <span class="ss">:option</span>

  <span class="c1"># you can also have dynamic settings with blocks</span>
  <span class="n">set</span><span class="p">(</span><span class="ss">:css_dir</span><span class="p">)</span> <span class="p">{</span> <span class="no">File</span><span class="p">.</span><span class="nf">join</span><span class="p">(</span><span class="n">views</span><span class="p">,</span> <span class="s1">'css'</span><span class="p">)</span> <span class="p">}</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Run only when the environment (<code>APP_ENV</code> environment variable) is set to
<code>:production</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">configure</span> <span class="ss">:production</span> <span class="k">do</span>
  <span class="o">...</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Run when the environment is set to either <code>:production</code> or <code>:test</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">configure</span> <span class="ss">:production</span><span class="p">,</span> <span class="ss">:test</span> <span class="k">do</span>
  <span class="o">...</span>
<span class="k">end</span>
</code></pre></div></div>

<p>You can access those options via <code>settings</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">configure</span> <span class="k">do</span>
  <span class="n">set</span> <span class="ss">:foo</span><span class="p">,</span> <span class="s1">'bar'</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="n">settings</span><span class="p">.</span><span class="nf">foo?</span> <span class="c1"># =&gt; true</span>
  <span class="n">settings</span><span class="p">.</span><span class="nf">foo</span>  <span class="c1"># =&gt; 'bar'</span>
  <span class="o">...</span>
<span class="k">end</span>
</code></pre></div></div>

<h3 id="configuring-attack-protection">Configuring attack protection</h3>

<p>Sinatra is using
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/sinatra/sinatra/tree/main/rack-protection#readme">Rack::Protection</a">https://github.com/sinatra/sinatra/tree/main/rack-protection#readme">Rack::Protection</a> to
defend your application against common, opportunistic attacks. You can
easily disable this behavior (which will open up your application to tons
of common vulnerabilities):</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">disable</span> <span class="ss">:protection</span>
</code></pre></div></div>

<p>To skip a single defense layer, set <code>protection</code> to an options hash:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:protection</span><span class="p">,</span> <span class="ss">:except</span> <span class="o">=&gt;</span> <span class="ss">:path_traversal</span>
</code></pre></div></div>
<p>You can also hand in an array in order to disable a list of protections:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:protection</span><span class="p">,</span> <span class="ss">:except</span> <span class="o">=&gt;</span> <span class="p">[</span><span class="ss">:path_traversal</span><span class="p">,</span> <span class="ss">:remote_token</span><span class="p">]</span>
</code></pre></div></div>

<p>By default, Sinatra will only set up session based protection if <code>:sessions</code>
have been enabled. See ‘<a href="#using-sessions">Using Sessions</a>’. Sometimes you may want to set up
sessions “outside” of the Sinatra app, such as in the config.ru or with a
separate <code>Rack::Builder</code> instance. In that case, you can still set up session
based protection by passing the <code>:session</code> option:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:protection</span><span class="p">,</span> <span class="ss">:session</span> <span class="o">=&gt;</span> <span class="kp">true</span>
</code></pre></div></div>

<h3 id="available-settings">Available Settings</h3>

<dl>
  <dt>absolute_redirects</dt>
    <dd>
      If disabled, Sinatra will allow relative redirects, however, Sinatra
      will no longer conform with RFC 2616 (HTTP 1.1), which only allows
      absolute redirects.
    </dd>
    <dd>
      Enable if your app is running behind a reverse proxy that has not been
      set up properly. Note that the <tt>url</tt> helper will still produce
      absolute URLs, unless you pass in <tt>false</tt> as the second
      parameter.
    </dd>
    <dd>Disabled by default.</dd>

  <dt>add_charset</dt>
    <dd>
      Mime types the <tt>content_type</tt> helper will automatically add the
      charset info to. You should add to it rather than overriding this
      option: <tt>settings.add_charset &lt;&lt; "application/foobar"</tt>
    </dd>

  <dt>app_file</dt>
    <dd>
      Path to the main application file, used to detect project root, views
      and public folder and inline templates.
    </dd>

  <dt>bind</dt>
    <dd>
      IP address to bind to (default: <tt>0.0.0.0</tt> <em>or</em>
      <tt>localhost</tt> if your `environment` is set to development). Only
      used for built-in server.
    </dd>

  <dt>default_content_type</dt>
  <dd>
    Content-Type to assume if unknown (defaults to <tt>"text/html"</tt>). Set
    to <tt>nil</tt> to not set a default Content-Type on every response; when
    configured so, you must set the Content-Type manually when emitting content
    or the user-agent will have to sniff it (or, if <tt>nosniff</tt> is enabled
    in Rack::Protection::XSSHeader, assume <tt>application/octet-stream</tt>).
  </dd>

  <dt>default_encoding</dt>
    <dd>Encoding to assume if unknown (defaults to <tt>"utf-8"</tt>).</dd>

  <dt>dump_errors</dt>
    <dd>Display errors in the log. Enabled by default unless environment is "test".</dd>

  <dt>environment</dt>
    <dd>
      Current environment. Defaults to <tt>ENV['APP_ENV']</tt>, or
      <tt>"development"</tt> if not available.
    </dd>

  <dt>host_authorization</dt>
  <dd>
    <p>
      You can pass a hash of options to <tt>host_authorization</tt>,
      to be used by the <tt>Rack::Protection::HostAuthorization</tt> middleware.
    </p>
    <p>
      The middleware can block requests with unrecognized hostnames, to prevent DNS rebinding
      and other host header attacks. It checks the <tt>Host</tt>, <tt>X-Forwarded-Host</tt>
      and <tt>Forwarded</tt> headers.
    </p>
    <p>
      Useful options are:
      </p>
<ul>
        <li>
<tt>permitted_hosts</tt> – an array of hostnames (and <tt>IPAddr</tt> objects) your app recognizes
          <ul>
            <li>in the <tt>development</tt> environment, it is set to <tt>.localhost</tt>, <tt>.test</tt> and any IPv4/IPv6 address</li>
            <li>if empty, any hostname is permitted (the default for any other environment)</li>
          </ul>
        </li>
        <li>
<tt>status</tt> – the HTTP status code used in the response when a request is blocked (defaults to <tt>403</tt>)</li>
        <li>
<tt>message</tt> – the body used in the response when a request is blocked (defaults to <tt>Host not permitted</tt>)</li>
        <li>
<tt>allow_if</tt> – supply a <tt>Proc</tt> to use custom allow/deny logic, the proc is passed the request environment</li>
      </ul>
    
  </dd>

  <dt>logging</dt>
    <dd>Use the logger.</dd>

  <dt>lock</dt>
    <dd>
      Places a lock around every request, only running processing on request
      per Ruby process concurrently.
    </dd>
    <dd>Enabled if your app is not thread-safe. Disabled by default.</dd>

  <dt>method_override</dt>
    <dd>
      Use <tt>_method</tt> magic to allow put/delete forms in browsers that
      don't support it.
    </dd>

  <dt>mustermann_opts</dt>
  <dd>
    A default hash of options to pass to Mustermann.new when compiling routing
    paths.
  </dd>

  <dt>port</dt>
    <dd>Port to listen on. Only used for built-in server.</dd>

  <dt>prefixed_redirects</dt>
    <dd>
      Whether or not to insert <tt>request.script_name</tt> into redirects
      if no absolute path is given. That way <tt>redirect '/foo'</tt> would
        behave like <tt>redirect to('/foo')</tt>. Disabled by default.
    </dd>

  <dt>protection</dt>
    <dd>
      Whether or not to enable web attack protections. See protection section
      above.
    </dd>

  <dt>public_dir</dt>
    <dd>Alias for <tt>public_folder</tt>. See below.</dd>

  <dt>public_folder</dt>
    <dd>
      Path to the folder public files are served from. Only used if static
      file serving is enabled (see <tt>static</tt> setting below). Inferred
      from <tt>app_file</tt> setting if not set.
    </dd>

  <dt>quiet</dt>
    <dd>
      Disables logs generated by Sinatra's start and stop commands.
      <tt>false</tt> by default.
    </dd>

  <dt>reload_templates</dt>
    <dd>
      Whether or not to reload templates between requests. Enabled in
      development mode.
    </dd>

  <dt>root</dt>
    <dd>
      Path to project root folder. Inferred from <tt>app_file</tt> setting
      if not set.
    </dd>

  <dt>raise_errors</dt>
    <dd>
      Raise unhandled errors (will stop application). Enabled by default when
      <tt>environment</tt> is set to <tt>"test"</tt>, disabled otherwise.
    </dd>
    <dd>
      Any explicitly defined error handlers always override this setting. See 
      the "Error" section below.
    </dd>

  <dt>run</dt>
    <dd>
      If enabled, Sinatra will handle starting the web server. Do not
      enable if using rackup or other means.
    </dd>

  <dt>running</dt>
    <dd>Is the built-in server running now? Do not change this setting!</dd>

  <dt>server</dt>
    <dd>
      Server or list of servers to use for built-in server. Order indicates
      priority, default depends on Ruby implementation.
    </dd>

  <dt>server_settings</dt>
    <dd>
      You can pass a hash of options to <tt>server_settings</tt>,
      such as <tt>Host</tt> or <tt>Port</tt>.
    </dd>

  <dt>sessions</dt>
    <dd>
      Enable cookie-based sessions support using
      <tt>Rack::Session::Cookie</tt>. See 'Using Sessions' section for more
      information.
    </dd>

  <dt>session_store</dt>
    <dd>
      The Rack session middleware used. Defaults to
      <tt>Rack::Session::Cookie</tt>. See 'Using Sessions' section for more
      information.
    </dd>

  <dt>show_exceptions</dt>
    <dd>
      Show a stack trace in the browser when an exception happens. Enabled by
      default when <tt>environment</tt> is set to <tt>"development"</tt>,
      disabled otherwise.
    </dd>
    <dd>
      Can also be set to <tt>:after_handler</tt> to trigger app-specified
      error handling before showing a stack trace in the browser.
    </dd>

  <dt>static</dt>
    <dd>Whether Sinatra should handle serving static files.</dd>
    <dd>Disable when using a server able to do this on its own.</dd>
    <dd>Disabling will boost performance.</dd>
    <dd>
      Enabled by default in classic style, disabled for modular apps.
    </dd>

  <dt>static_cache_control</dt>
    <dd>
      When Sinatra is serving static files, set this to add
      <tt>Cache-Control</tt> headers to the responses. Uses the
      <tt>cache_control</tt> helper. Disabled by default.
    </dd>
    <dd>
      Use an explicit array when setting multiple values:
      <tt>set :static_cache_control, [:public, :max_age =&gt; 300]</tt>
    </dd>

  <dt>threaded</dt>
    <dd>
      If set to <tt>true</tt>, will tell server to use
      <tt>EventMachine.defer</tt> for processing the request.
    </dd>

  <dt>traps</dt>
    <dd>Whether Sinatra should handle system signals.</dd>

  <dt>views</dt>
    <dd>
      Path to the views folder. Inferred from <tt>app_file</tt> setting if
      not set.
    </dd>

  <dt>x_cascade</dt>
    <dd>
      Whether or not to set the X-Cascade header if no route matches.
      Defaults to <tt>true</tt>.
    </dd>
</dl>

<h2 id="lifecycle-events">Lifecycle Events</h2>

<p>There are 2 lifecycle events currently exposed by Sinatra. One when the server starts and one when it stops.</p>

<p>They can be used like this:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">on_start</span> <span class="k">do</span>
  <span class="nb">puts</span> <span class="s2">"===== Booting up ====="</span>
<span class="k">end</span>

<span class="n">on_stop</span> <span class="k">do</span>
  <span class="nb">puts</span> <span class="s2">"===== Shutting down ====="</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Note that these callbacks only work when using Sinatra to start the web server.</p>

<h2 id="environments">Environments</h2>

<p>There are three predefined <code>environments</code>: <code>"development"</code>,
<code>"production"</code> and <code>"test"</code>. Environments can be set through the
<code>APP_ENV</code> environment variable. The default value is <code>"development"</code>.
In the <code>"development"</code> environment all templates are reloaded between
requests, and special <code>not_found</code> and <code>error</code> handlers display stack
traces in your browser. In the <code>"production"</code> and <code>"test"</code> environments,
templates are cached by default.</p>

<p>To run different environments, set the <code>APP_ENV</code> environment variable:</p>

<div class="language-shell highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nv">APP_ENV</span><span class="o">=</span>production ruby my_app.rb
</code></pre></div></div>

<p>You can use predefined methods: <code>development?</code>, <code>test?</code> and <code>production?</code> to
check the current environment setting:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="k">if</span> <span class="n">settings</span><span class="p">.</span><span class="nf">development?</span>
    <span class="s2">"development!"</span>
  <span class="k">else</span>
    <span class="s2">"not development!"</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<h2 id="error-handling">Error Handling</h2>

<p>Error handlers run within the same context as routes and before filters,
which means you get all the goodies it has to offer, like <code>haml</code>, <code>erb</code>,
<code>halt</code>, etc.</p>

<h3 id="not-found">Not Found</h3>

<p>When a <code>Sinatra::NotFound</code> exception is raised, or the response’s status
code is 404, the <code>not_found</code> handler is invoked:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">not_found</span> <span class="k">do</span>
  <span class="s1">'This is nowhere to be found.'</span>
<span class="k">end</span>
</code></pre></div></div>

<h3 id="error">Error</h3>

<p>The <code>error</code> handler is invoked any time an exception is raised from a route
block or a filter. But note in development it will only run if you set the
show exceptions option to <code>:after_handler</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">set</span> <span class="ss">:show_exceptions</span><span class="p">,</span> <span class="ss">:after_handler</span>
</code></pre></div></div>

<p>A catch-all error handler can be defined with <code>error</code> and a block:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">error</span> <span class="k">do</span>
  <span class="s1">'Sorry there was a nasty error'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>The exception object can be obtained from the <code>sinatra.error</code> Rack variable:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">error</span> <span class="k">do</span>
  <span class="s1">'Sorry there was a nasty error - '</span> <span class="o">+</span> <span class="n">env</span><span class="p">[</span><span class="s1">'sinatra.error'</span><span class="p">].</span><span class="nf">message</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Pass an error class as an argument to create handlers for custom errors:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">error</span> <span class="no">MyCustomError</span> <span class="k">do</span>
  <span class="s1">'So what happened was...'</span> <span class="o">+</span> <span class="n">env</span><span class="p">[</span><span class="s1">'sinatra.error'</span><span class="p">].</span><span class="nf">message</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Then, if this happens:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="k">raise</span> <span class="no">MyCustomError</span><span class="p">,</span> <span class="s1">'something bad'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>You get this:</p>

<pre><code>So what happened was... something bad
</code></pre>

<p>Alternatively, you can install an error handler for a status code:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">error</span> <span class="mi">403</span> <span class="k">do</span>
  <span class="s1">'Access forbidden'</span>
<span class="k">end</span>

<span class="n">get</span> <span class="s1">'/secret'</span> <span class="k">do</span>
  <span class="mi">403</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Or a range:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">error</span> <span class="mi">400</span><span class="o">..</span><span class="mi">510</span> <span class="k">do</span>
  <span class="s1">'Boom'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Sinatra installs special <code>not_found</code> and <code>error</code> handlers when
running under the development environment to display nice stack traces
and additional debugging information in your browser.</p>

<h3 id="behavior-with-raiseerrors-option">Behavior with <code>raise_errors</code> option</h3>

<p>When <code>raise_errors</code> option is <code>true</code>, errors that are unhandled are raised 
outside of the application. Additionally, any errors that would have been 
caught by the catch-all error handler are raised.</p>

<p>For example, consider the following configuration:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># First handler</span>
<span class="n">error</span> <span class="no">MyCustomError</span> <span class="k">do</span>
  <span class="s1">'A custom message'</span>
<span class="k">end</span>

<span class="c1"># Second handler</span>
<span class="n">error</span> <span class="k">do</span>
  <span class="s1">'A catch-all message'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>If <code>raise_errors</code> is <code>false</code>:</p>

<ul>
  <li>When <code>MyCustomError</code> or descendant is raised, the first handler is invoked.
The HTTP response body will contain <code>"A custom message"</code>.</li>
  <li>When any other error is raised, the second handler is invoked. The HTTP 
response body will contain <code>"A catch-all message"</code>.</li>
</ul>

<p>If <code>raise_errors</code> is <code>true</code>:</p>

<ul>
  <li>When <code>MyCustomError</code> or descendant is raised, the behavior is identical to 
when <code>raise_errors</code> is <code>false</code>, described above.</li>
  <li>When any other error is raised, the second handler is <em>not</em> invoked, and 
the error is raised outside of the application.
    <ul>
      <li>If the environment is <code>production</code>, the HTTP response body will contain 
a generic error message, e.g. <code>"An unhandled lowlevel error occurred. The
application logs may have details."</code>
</li>
      <li>If the environment is not <code>production</code>, the HTTP response body will contain
the verbose error backtrace.</li>
      <li>Regardless of environment, if <code>show_exceptions</code> is set to <code>:after_handler</code>, 
the HTTP response body will contain the verbose error backtrace.</li>
    </ul>
  </li>
</ul>

<p>In the <code>test</code> environment, <code>raise_errors</code> is set to <code>true</code> by default. This 
means that in order to write a test for a catch-all error handler, 
<code>raise_errors</code> must temporarily be set to <code>false</code> for that particular test.</p>

<h2 id="rack-middleware">Rack Middleware</h2>

<p>Sinatra rides on <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://rack.github.io/">Rack</a" rel="nofollow">https://rack.github.io/">Rack</a>, a minimal standard
interface for Ruby web frameworks. One of Rack’s most interesting
capabilities for application developers is support for “middleware” –
components that sit between the server and your application monitoring
and/or manipulating the HTTP request/response to provide various types
of common functionality.</p>

<p>Sinatra makes building Rack middleware pipelines a cinch via a top-level
<code>use</code> method:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'sinatra'</span>
<span class="nb">require</span> <span class="s1">'my_custom_middleware'</span>

<span class="n">use</span> <span class="no">Rack</span><span class="o">::</span><span class="no">Lint</span>
<span class="n">use</span> <span class="no">MyCustomMiddleware</span>

<span class="n">get</span> <span class="s1">'/hello'</span> <span class="k">do</span>
  <span class="s1">'Hello World'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>The semantics of <code>use</code> are identical to those defined for the
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://www.rubydoc.info/github/rack/rack/main/Rack/Builder">Rack::Builder</a" rel="nofollow">https://www.rubydoc.info/github/rack/rack/main/Rack/Builder">Rack::Builder</a> DSL
(most frequently used from rackup files). For example, the <code>use</code> method
accepts multiple/variable args as well as blocks:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">use</span> <span class="no">Rack</span><span class="o">::</span><span class="no">Auth</span><span class="o">::</span><span class="no">Basic</span> <span class="k">do</span> <span class="o">|</span><span class="n">username</span><span class="p">,</span> <span class="n">password</span><span class="o">|</span>
  <span class="n">username</span> <span class="o">==</span> <span class="s1">'admin'</span> <span class="o">&amp;&amp;</span> <span class="n">password</span> <span class="o">==</span> <span class="s1">'secret'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Rack is distributed with a variety of standard middleware for logging,
debugging, URL routing, authentication, and session handling. Sinatra uses
many of these components automatically based on configuration so you
typically don’t have to <code>use</code> them explicitly.</p>

<p>You can find useful middleware in
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/rack/rack/tree/main/lib/rack">rack</a">https://github.com/rack/rack/tree/main/lib/rack">rack</a>,
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/rack/rack-contrib#readme">rack-contrib</a">https://github.com/rack/rack-contrib#readme">rack-contrib</a>,
or in the <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/rack/rack/wiki/List-of-Middleware">Rack">https://github.com/rack/rack/wiki/List-of-Middleware">Rack wiki</a>.</p>

<h2 id="testing">Testing</h2>

<p>Sinatra tests can be written using any Rack-based testing library or
framework.
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://www.rubydoc.info/github/rack/rack-test/main/frames">Rack::Test</a" rel="nofollow">https://www.rubydoc.info/github/rack/rack-test/main/frames">Rack::Test</a>
is recommended:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'my_sinatra_app'</span>
<span class="nb">require</span> <span class="s1">'minitest/autorun'</span>
<span class="nb">require</span> <span class="s1">'rack/test'</span>

<span class="k">class</span> <span class="nc">MyAppTest</span> <span class="o">&lt;</span> <span class="no">Minitest</span><span class="o">::</span><span class="no">Test</span>
  <span class="kp">include</span> <span class="no">Rack</span><span class="o">::</span><span class="no">Test</span><span class="o">::</span><span class="no">Methods</span>

  <span class="k">def</span> <span class="nf">app</span>
    <span class="no">Sinatra</span><span class="o">::</span><span class="no">Application</span>
  <span class="k">end</span>

  <span class="k">def</span> <span class="nf">test_my_default</span>
    <span class="n">get</span> <span class="s1">'/'</span>
    <span class="n">assert_equal</span> <span class="s1">'Hello World!'</span><span class="p">,</span> <span class="n">last_response</span><span class="p">.</span><span class="nf">body</span>
  <span class="k">end</span>

  <span class="k">def</span> <span class="nf">test_with_params</span>
    <span class="n">get</span> <span class="s1">'/meet'</span><span class="p">,</span> <span class="ss">:name</span> <span class="o">=&gt;</span> <span class="s1">'Frank'</span>
    <span class="n">assert_equal</span> <span class="s1">'Hello Frank!'</span><span class="p">,</span> <span class="n">last_response</span><span class="p">.</span><span class="nf">body</span>
  <span class="k">end</span>

  <span class="k">def</span> <span class="nf">test_with_user_agent</span>
    <span class="n">get</span> <span class="s1">'/'</span><span class="p">,</span> <span class="p">{},</span> <span class="s1">'HTTP_USER_AGENT'</span> <span class="o">=&gt;</span> <span class="s1">'Songbird'</span>
    <span class="n">assert_equal</span> <span class="s2">"You're using Songbird!"</span><span class="p">,</span> <span class="n">last_response</span><span class="p">.</span><span class="nf">body</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Note: If you are using Sinatra in the modular style, replace
<code>Sinatra::Application</code> above with the class name of your app.</p>

<h2 id="sinatrabase---middleware-libraries-and-modular-apps">Sinatra::Base - Middleware, Libraries, and Modular Apps</h2>

<p>Defining your app at the top-level works well for micro-apps but has
considerable drawbacks when building reusable components such as Rack
middleware, Rails metal, simple libraries with a server component, or even
Sinatra extensions. The top-level assumes a micro-app style configuration
(e.g., a single application file, <code>./public</code> and <code>./views</code>
directories, logging, exception detail page, etc.). That’s where
<code>Sinatra::Base</code> comes into play:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'sinatra/base'</span>

<span class="k">class</span> <span class="nc">MyApp</span> <span class="o">&lt;</span> <span class="no">Sinatra</span><span class="o">::</span><span class="no">Base</span>
  <span class="n">set</span> <span class="ss">:sessions</span><span class="p">,</span> <span class="kp">true</span>
  <span class="n">set</span> <span class="ss">:foo</span><span class="p">,</span> <span class="s1">'bar'</span>

  <span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
    <span class="s1">'Hello world!'</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<p>The methods available to <code>Sinatra::Base</code> subclasses are exactly the same
as those available via the top-level DSL. Most top-level apps can be
converted to <code>Sinatra::Base</code> components with two modifications:</p>

<ul>
  <li>Your file should require <code>sinatra/base</code> instead of <code>sinatra</code>;
otherwise, all of Sinatra’s DSL methods are imported into the main
namespace.</li>
  <li>Put your app’s routes, error handlers, filters, and options in a subclass
of <code>Sinatra::Base</code>.</li>
</ul>

<p><code>Sinatra::Base</code> is a blank slate. Most options are disabled by default,
including the built-in server. See <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"http://www.sinatrarb.com/configuration.html">Configuring" rel="nofollow">http://www.sinatrarb.com/configuration.html">Configuring
Settings</a> for details on
available options and their behavior. If you want behavior more similar
to when you define your app at the top level (also known as Classic
style), you can subclass <code>Sinatra::Application</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'sinatra/base'</span>

<span class="k">class</span> <span class="nc">MyApp</span> <span class="o">&lt;</span> <span class="no">Sinatra</span><span class="o">::</span><span class="no">Application</span>
  <span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
    <span class="s1">'Hello world!'</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<h3 id="modular-vs-classic-style">Modular vs. Classic Style</h3>

<p>Contrary to common belief, there is nothing wrong with the classic
style. If it suits your application, you do not have to switch to a
modular application.</p>

<p>The main disadvantage of using the classic style rather than the modular
style is that you will only have one Sinatra application per Ruby
process. If you plan to use more than one, switch to the modular style.
There is no reason you cannot mix the modular and classic styles.</p>

<p>If switching from one style to the other, you should be aware of
slightly different default settings:</p>

<table>
  <tr>
    <th>Setting</th>
    <th>Classic</th>
    <th>Modular</th>
    <th>Modular</th>
  </tr>

  <tr>
    <td>app_file</td>
    <td>file loading sinatra</td>
    <td>file subclassing Sinatra::Base</td>
    <td>file subclassing Sinatra::Application</td>
  </tr>

  <tr>
    <td>run</td>
    <td>$0 == app_file</td>
    <td>false</td>
    <td>false</td>
  </tr>

  <tr>
    <td>logging</td>
    <td>true</td>
    <td>false</td>
    <td>true</td>
  </tr>

  <tr>
    <td>method_override</td>
    <td>true</td>
    <td>false</td>
    <td>true</td>
  </tr>

  <tr>
    <td>inline_templates</td>
    <td>true</td>
    <td>false</td>
    <td>true</td>
  </tr>

  <tr>
    <td>static</td>
    <td>true</td>
    <td>File.exist?(public_folder)</td>
    <td>true</td>
  </tr>
</table>

<h3 id="serving-a-modular-application">Serving a Modular Application</h3>

<p>There are two common options for starting a modular app, actively
starting with <code>run!</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># my_app.rb</span>
<span class="nb">require</span> <span class="s1">'sinatra/base'</span>

<span class="k">class</span> <span class="nc">MyApp</span> <span class="o">&lt;</span> <span class="no">Sinatra</span><span class="o">::</span><span class="no">Base</span>
  <span class="c1"># ... app code here ...</span>

  <span class="c1"># start the server if ruby file executed directly</span>
  <span class="n">run!</span> <span class="k">if</span> <span class="n">app_file</span> <span class="o">==</span> <span class="vg">$0</span>
<span class="k">end</span>
</code></pre></div></div>

<p>Start with:</p>

<div class="language-shell highlighter-rouge"><div class="highlight"><pre class="highlight"><code>ruby my_app.rb
</code></pre></div></div>

<p>Or with a <code>config.ru</code> file, which allows using any Rack handler:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># config.ru (run with rackup)</span>
<span class="nb">require</span> <span class="s1">'./my_app'</span>
<span class="n">run</span> <span class="no">MyApp</span>
</code></pre></div></div>

<p>Run:</p>

<div class="language-shell highlighter-rouge"><div class="highlight"><pre class="highlight"><code>rackup <span class="nt">-p</span> 4567
</code></pre></div></div>

<h3 id="using-a-classic-style-application-with-a-configru">Using a Classic Style Application with a config.ru</h3>

<p>Write your app file:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># app.rb</span>
<span class="nb">require</span> <span class="s1">'sinatra'</span>

<span class="n">get</span> <span class="s1">'/'</span> <span class="k">do</span>
  <span class="s1">'Hello world!'</span>
<span class="k">end</span>
</code></pre></div></div>

<p>And a corresponding <code>config.ru</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'./app'</span>
<span class="n">run</span> <span class="no">Sinatra</span><span class="o">::</span><span class="no">Application</span>
</code></pre></div></div>

<h3 id="when-to-use-a-configru">When to use a config.ru?</h3>

<p>A <code>config.ru</code> file is recommended if:</p>

<ul>
  <li>You want to deploy with a different Rack handler (Passenger, Unicorn,
Heroku, …).</li>
  <li>You want to use more than one subclass of <code>Sinatra::Base</code>.</li>
  <li>You want to use Sinatra only for middleware, and not as an endpoint.</li>
</ul>

<p><strong>There is no need to switch to a <code>config.ru</code> simply because you
switched to the modular style, and you don’t have to use the modular
style for running with a <code>config.ru</code>.</strong></p>

<h3 id="using-sinatra-as-middleware">Using Sinatra as Middleware</h3>

<p>Not only is Sinatra able to use other Rack middleware, any Sinatra
application can, in turn, be added in front of any Rack endpoint as
middleware itself. This endpoint could be another Sinatra application,
or any other Rack-based application (Rails/Hanami/Roda/…):</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'sinatra/base'</span>

<span class="k">class</span> <span class="nc">LoginScreen</span> <span class="o">&lt;</span> <span class="no">Sinatra</span><span class="o">::</span><span class="no">Base</span>
  <span class="n">enable</span> <span class="ss">:sessions</span>

  <span class="n">get</span><span class="p">(</span><span class="s1">'/login'</span><span class="p">)</span> <span class="p">{</span> <span class="n">haml</span> <span class="ss">:login</span> <span class="p">}</span>

  <span class="n">post</span><span class="p">(</span><span class="s1">'/login'</span><span class="p">)</span> <span class="k">do</span>
    <span class="k">if</span> <span class="n">params</span><span class="p">[</span><span class="s1">'name'</span><span class="p">]</span> <span class="o">==</span> <span class="s1">'admin'</span> <span class="o">&amp;&amp;</span> <span class="n">params</span><span class="p">[</span><span class="s1">'password'</span><span class="p">]</span> <span class="o">==</span> <span class="s1">'admin'</span>
      <span class="n">session</span><span class="p">[</span><span class="s1">'user_name'</span><span class="p">]</span> <span class="o">=</span> <span class="n">params</span><span class="p">[</span><span class="s1">'name'</span><span class="p">]</span>
    <span class="k">else</span>
      <span class="n">redirect</span> <span class="s1">'/login'</span>
    <span class="k">end</span>
  <span class="k">end</span>
<span class="k">end</span>

<span class="k">class</span> <span class="nc">MyApp</span> <span class="o">&lt;</span> <span class="no">Sinatra</span><span class="o">::</span><span class="no">Base</span>
  <span class="c1"># middleware will run before filters</span>
  <span class="n">use</span> <span class="no">LoginScreen</span>

  <span class="n">before</span> <span class="k">do</span>
    <span class="k">unless</span> <span class="n">session</span><span class="p">[</span><span class="s1">'user_name'</span><span class="p">]</span>
      <span class="n">halt</span> <span class="s2">"Access denied, please &lt;a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Flogin"&gt;login&lt;/a&gt;."</span>
    <span class="k">end</span>
  <span class="k">end</span>

  <span class="n">get</span><span class="p">(</span><span class="s1">'/'</span><span class="p">)</span> <span class="p">{</span> <span class="s2">"Hello </span><span class="si">#{</span><span class="n">session</span><span class="p">[</span><span class="s1">'user_name'</span><span class="p">]</span><span class="si">}</span><span class="s2">."</span> <span class="p">}</span>
<span class="k">end</span>
</code></pre></div></div>

<h3 id="dynamic-application-creation">Dynamic Application Creation</h3>

<p>Sometimes you want to create new applications at runtime without having to
assign them to a constant. You can do this with <code>Sinatra.new</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'sinatra/base'</span>
<span class="n">my_app</span> <span class="o">=</span> <span class="no">Sinatra</span><span class="p">.</span><span class="nf">new</span> <span class="p">{</span> <span class="n">get</span><span class="p">(</span><span class="s1">'/'</span><span class="p">)</span> <span class="p">{</span> <span class="s2">"hi"</span> <span class="p">}</span> <span class="p">}</span>
<span class="n">my_app</span><span class="p">.</span><span class="nf">run!</span>
</code></pre></div></div>

<p>It takes the application to inherit from as an optional argument:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># config.ru (run with rackup)</span>
<span class="nb">require</span> <span class="s1">'sinatra/base'</span>

<span class="n">controller</span> <span class="o">=</span> <span class="no">Sinatra</span><span class="p">.</span><span class="nf">new</span> <span class="k">do</span>
  <span class="n">enable</span> <span class="ss">:logging</span>
  <span class="n">helpers</span> <span class="no">MyHelpers</span>
<span class="k">end</span>

<span class="n">map</span><span class="p">(</span><span class="s1">'/a'</span><span class="p">)</span> <span class="k">do</span>
  <span class="n">run</span> <span class="no">Sinatra</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="n">controller</span><span class="p">)</span> <span class="p">{</span> <span class="n">get</span><span class="p">(</span><span class="s1">'/'</span><span class="p">)</span> <span class="p">{</span> <span class="s1">'a'</span> <span class="p">}</span> <span class="p">}</span>
<span class="k">end</span>

<span class="n">map</span><span class="p">(</span><span class="s1">'/b'</span><span class="p">)</span> <span class="k">do</span>
  <span class="n">run</span> <span class="no">Sinatra</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="n">controller</span><span class="p">)</span> <span class="p">{</span> <span class="n">get</span><span class="p">(</span><span class="s1">'/'</span><span class="p">)</span> <span class="p">{</span> <span class="s1">'b'</span> <span class="p">}</span> <span class="p">}</span>
<span class="k">end</span>
</code></pre></div></div>

<p>This is especially useful for testing Sinatra extensions or using Sinatra in
your own library.</p>

<p>This also makes using Sinatra as middleware extremely easy:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'sinatra/base'</span>

<span class="n">use</span> <span class="no">Sinatra</span> <span class="k">do</span>
  <span class="n">get</span><span class="p">(</span><span class="s1">'/'</span><span class="p">)</span> <span class="p">{</span> <span class="o">...</span> <span class="p">}</span>
<span class="k">end</span>

<span class="n">run</span> <span class="no">RailsProject</span><span class="o">::</span><span class="no">Application</span>
</code></pre></div></div>

<h2 id="scopes-and-binding">Scopes and Binding</h2>

<p>The scope you are currently in determines what methods and variables are
available.</p>

<h3 id="applicationclass-scope">Application/Class Scope</h3>

<p>Every Sinatra application corresponds to a subclass of <code>Sinatra::Base</code>.
If you are using the top-level DSL (<code>require 'sinatra'</code>), then this
class is <code>Sinatra::Application</code>, otherwise it is the subclass you
created explicitly. At the class level, you have methods like <code>get</code> or
<code>before</code>, but you cannot access the <code>request</code> or <code>session</code> objects, as
there is only a single application class for all requests.</p>

<p>Options created via <code>set</code> are methods at class level:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="nc">MyApp</span> <span class="o">&lt;</span> <span class="no">Sinatra</span><span class="o">::</span><span class="no">Base</span>
  <span class="c1"># Hey, I'm in the application scope!</span>
  <span class="n">set</span> <span class="ss">:foo</span><span class="p">,</span> <span class="mi">42</span>
  <span class="n">foo</span> <span class="c1"># =&gt; 42</span>

  <span class="n">get</span> <span class="s1">'/foo'</span> <span class="k">do</span>
    <span class="c1"># Hey, I'm no longer in the application scope!</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<p>You have the application scope binding inside:</p>

<ul>
  <li>Your application class body</li>
  <li>Methods defined by extensions</li>
  <li>The block passed to <code>helpers</code>
</li>
  <li>Procs/blocks used as a value for <code>set</code>
</li>
  <li>The block passed to <code>Sinatra.new</code>
</li>
</ul>

<p>You can reach the scope object (the class) like this:</p>

<ul>
  <li>Via the object passed to configure blocks (<code>configure { |c| ... }</code>)</li>
  <li>
<code>settings</code> from within the request scope</li>
</ul>

<h3 id="requestinstance-scope">Request/Instance Scope</h3>

<p>For every incoming request, a new instance of your application class is
created, and all handler blocks run in that scope. From within this scope you
can access the <code>request</code> and <code>session</code> objects or call rendering methods like
<code>erb</code> or <code>haml</code>. You can access the application scope from within the request
scope via the <code>settings</code> helper:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="nc">MyApp</span> <span class="o">&lt;</span> <span class="no">Sinatra</span><span class="o">::</span><span class="no">Base</span>
  <span class="c1"># Hey, I'm in the application scope!</span>
  <span class="n">get</span> <span class="s1">'/define_route/:name'</span> <span class="k">do</span>
    <span class="c1"># Request scope for '/define_route/:name'</span>
    <span class="vi">@value</span> <span class="o">=</span> <span class="mi">42</span>

    <span class="n">settings</span><span class="p">.</span><span class="nf">get</span><span class="p">(</span><span class="s2">"/</span><span class="si">#{</span><span class="n">params</span><span class="p">[</span><span class="s1">'name'</span><span class="p">]</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span> <span class="k">do</span>
      <span class="c1"># Request scope for "/#{params['name']}"</span>
      <span class="vi">@value</span> <span class="c1"># =&gt; nil (not the same request)</span>
    <span class="k">end</span>

    <span class="s2">"Route defined!"</span>
  <span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div>

<p>You have the request scope binding inside:</p>

<ul>
  <li>get, head, post, put, delete, options, patch, link and unlink blocks</li>
  <li>before and after filters</li>
  <li>helper methods</li>
  <li>templates/views</li>
</ul>

<h3 id="delegation-scope">Delegation Scope</h3>

<p>The delegation scope just forwards methods to the class scope. However, it
does not behave exactly like the class scope, as you do not have the class
binding. Only methods explicitly marked for delegation are available, and you
do not share variables/state with the class scope (read: you have a different
<code>self</code>). You can explicitly add method delegations by calling
<code>Sinatra::Delegator.delegate :method_name</code>.</p>

<p>You have the delegate scope binding inside:</p>

<ul>
  <li>The top-level binding, if you did <code>require "sinatra"</code>
</li>
  <li>An object extended with the <code>Sinatra::Delegator</code> mixin</li>
</ul>

<p>Have a look at the code for yourself: here’s the
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/sinatra/sinatra/blob/ca06364/lib/sinatra/base.rb#L1609-1633">Sinatra::Delegator">https://github.com/sinatra/sinatra/blob/ca06364/lib/sinatra/base.rb#L1609-1633">Sinatra::Delegator mixin</a>
being <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/sinatra/sinatra/blob/ca06364/lib/sinatra/main.rb#L28-30">extending">https://github.com/sinatra/sinatra/blob/ca06364/lib/sinatra/main.rb#L28-30">extending the main object</a>.</p>

<h2 id="command-line">Command Line</h2>

<p>Sinatra applications can be run directly:</p>

<div class="language-shell highlighter-rouge"><div class="highlight"><pre class="highlight"><code>ruby myapp.rb <span class="o">[</span><span class="nt">-h</span><span class="o">]</span> <span class="o">[</span><span class="nt">-x</span><span class="o">]</span> <span class="o">[</span><span class="nt">-q</span><span class="o">]</span> <span class="o">[</span><span class="nt">-e</span> ENVIRONMENT] <span class="o">[</span><span class="nt">-p</span> PORT] <span class="o">[</span><span class="nt">-o</span> HOST] <span class="o">[</span><span class="nt">-s</span> HANDLER]
</code></pre></div></div>

<p>Options are:</p>

<pre><code>-h # help
-p # set the port (default is 4567)
-o # set the host (default is 0.0.0.0)
-e # set the environment (default is development)
-s # specify rack server/handler (default is puma)
-q # turn on quiet mode for server (default is off)
-x # turn on the mutex lock (default is off)
</code></pre>

<h3 id="multi-threading">Multi-threading</h3>

<p><em>Paraphrasing from
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://stackoverflow.com/a/6282999/5245129">this" rel="nofollow">https://stackoverflow.com/a/6282999/5245129">this StackOverflow answer</a>
by Konstantin</em></p>

<p>Sinatra doesn’t impose any concurrency model but leaves that to the
underlying Rack handler (server) like Puma or Falcon. Sinatra
itself is thread-safe, so there won’t be any problem if the Rack handler
uses a threaded model of concurrency.</p>

<h2 id="requirement">Requirement</h2>

<p>The following Ruby versions are officially supported:</p>
<dl>
  <dt>Ruby</dt>
  <dd>
    <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://www.ruby-lang.org/en/downloads/">The" rel="nofollow">https://www.ruby-lang.org/en/downloads/">The stable releases</a> are fully supported and recommended.
  </dd>

  <dt>TruffleRuby</dt>
  <dd>
    The latest stable release of TruffleRuby is supported.
  </dd>

  <dt>JRuby</dt>
  <dd>
    The latest stable release of JRuby is supported. It is not
    recommended to use C extensions with JRuby.
  </dd>
</dl>

<p>Versions of Ruby before 2.7.8 are no longer supported as of Sinatra 4.0.0.</p>

<p>Sinatra should work on any operating system supported by the chosen Ruby
implementation.</p>

<p>Running Sinatra on a not officially supported Ruby flavor means that if things only break there we assume it’s not our issue but theirs.</p>

<h2 id="the-bleeding-edge">The Bleeding Edge</h2>

<p>If you would like to use Sinatra’s latest bleeding-edge code, feel free
to run your application against the main branch, it should be rather
stable.</p>

<p>We also push out prerelease gems from time to time, so you can do a</p>

<div class="language-shell highlighter-rouge"><div class="highlight"><pre class="highlight"><code>gem <span class="nb">install </span>sinatra <span class="nt">--pre</span>
</code></pre></div></div>

<p>to get some of the latest features.</p>

<h3 id="with-bundler">With Bundler</h3>

<p>If you want to run your application with the latest Sinatra, using
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://bundler.io">Bundler</a" rel="nofollow">https://bundler.io">Bundler</a> is the recommended way.</p>

<p>First, install bundler, if you haven’t:</p>

<div class="language-shell highlighter-rouge"><div class="highlight"><pre class="highlight"><code>gem <span class="nb">install </span>bundler
</code></pre></div></div>

<p>Then, in your project directory, create a <code>Gemfile</code>:</p>

<div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">source</span> <span class="s1">'https://rubygems.org'</span>
<span class="n">gem</span> <span class="s1">'sinatra'</span><span class="p">,</span> <span class="ss">:github</span> <span class="o">=&gt;</span> <span class="s1">'sinatra/sinatra'</span>

<span class="c1"># other dependencies</span>
<span class="n">gem</span> <span class="s1">'haml'</span>                    <span class="c1"># for instance, if you use haml</span>
</code></pre></div></div>

<p>Note that you will have to list all your application’s dependencies in
the <code>Gemfile</code>. Sinatra’s direct dependencies (Rack and Tilt) will,
however, be automatically fetched and added by Bundler.</p>

<p>Now you can run your app like this:</p>

<div class="language-shell highlighter-rouge"><div class="highlight"><pre class="highlight"><code>bundle <span class="nb">exec </span>ruby myapp.rb
</code></pre></div></div>

<h2 id="versioning">Versioning</h2>

<p>Sinatra follows <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://semver.org/">Semantic" rel="nofollow">https://semver.org/">Semantic Versioning</a>, both SemVer and
SemVerTag.</p>

<h2 id="further-reading">Further Reading</h2>

<ul>
  <li>
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://sinatrarb.com/">Project" rel="nofollow">https://sinatrarb.com/">Project Website</a> - Additional documentation,
news, and links to other resources.</li>
  <li>
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://sinatrarb.com/contributing">Contributing</a" rel="nofollow">https://sinatrarb.com/contributing">Contributing</a> - Find a bug? Need
help? Have a patch?</li>
  <li><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/sinatra/sinatra/issues">Issue">https://github.com/sinatra/sinatra/issues">Issue tracker</a></li>
  <li><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://twitter.com/sinatra">Twitter</a></li" rel="nofollow">https://twitter.com/sinatra">Twitter</a></li>
  <li><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://groups.google.com/forum/#!forum/sinatrarb">Mailing" rel="nofollow">https://groups.google.com/forum/#!forum/sinatrarb">Mailing List</a></li>
  <li>IRC: <a href="/deoxy?target=irc%3A%2F%2Fchat.freenode.net%2F%23sinatra">#sinatra</a> on <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://freenode.net">Freenode</a" rel="nofollow">https://freenode.net">Freenode</a>
</li>
  <li>
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://discord.gg/ncjsfsNHh7">Sinatra" rel="nofollow">https://discord.gg/ncjsfsNHh7">Sinatra &amp; Friends</a> on Discord</li>
  <li>
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/sinatra/sinatra-book">Sinatra">https://github.com/sinatra/sinatra-book">Sinatra Book</a> - Cookbook Tutorial</li>
  <li>
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"http://recipes.sinatrarb.com/">Sinatra" rel="nofollow">http://recipes.sinatrarb.com/">Sinatra Recipes</a> - Community contributed
recipes</li>
  <li>API documentation for the <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://www.rubydoc.info/gems/sinatra">latest" rel="nofollow">https://www.rubydoc.info/gems/sinatra">latest release</a>
or the <a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://www.rubydoc.info/github/sinatra/sinatra">current" rel="nofollow">https://www.rubydoc.info/github/sinatra/sinatra">current HEAD</a> on
<a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://www.rubydoc.info/">RubyDoc</a" rel="nofollow">https://www.rubydoc.info/">RubyDoc</a>
</li>
  <li><a href="/deoxy?target=https%3A%2F%2Fgithub.com%2Fsinatra%2Fsinatra.github.com%2Ftree%2Fmain%2F%253Ca%2520href%3D"https://github.com/sinatra/sinatra/actions">CI">https://github.com/sinatra/sinatra/actions">CI Actions</a></li>
</ul>
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