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<title>Class: Rack::Builder</title>
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<div id="classHeader">
<table class="header-table">
<tr class="top-aligned-row">
<td><strong>Class</strong></td>
<td class="class-name-in-header">Rack::Builder</td>
</tr>
<tr class="top-aligned-row">
<td><strong>In:</strong></td>
<td>
<a href="../../files/lib/rack/builder_rb.html">
lib/rack/builder.rb
</a>
<br />
</td>
</tr>
<tr class="top-aligned-row">
<td><strong>Parent:</strong></td>
<td>
Object
</td>
</tr>
</table>
</div>
<!-- banner header -->
<div id="bodyContent">
<div id="contextContent">
<div id="description">
<p>
<a href="Builder.html">Rack::Builder</a> implements a small DSL to
iteratively construct <a href="../Rack.html">Rack</a> applications.
</p>
<p>
Example:
</p>
<pre>
require 'rack/lobster'
app = Rack::Builder.new do
use Rack::CommonLogger
use Rack::ShowExceptions
map "/lobster" do
use Rack::Lint
run Rack::Lobster.new
end
end
run app
</pre>
<p>
Or
</p>
<pre>
app = Rack::Builder.app do
use Rack::CommonLogger
run lambda { |env| [200, {'Content-Type' => 'text/plain'}, ['OK']] }
end
run app
</pre>
<p>
<tt><a href="Builder.html#M000390">use</a></tt> adds middleware to the
stack, <tt><a href="Builder.html#M000391">run</a></tt> dispatches to an
application. You can <a href="Builder.html#M000390">use</a> <tt><a
href="Builder.html#M000393">map</a></tt> to construct a <a
href="URLMap.html">Rack::URLMap</a> in a convenient way.
</p>
</div>
</div>
<div id="method-list">
<h3 class="section-bar">Methods</h3>
<div class="name-list">
<a href="#M000389">app</a>
<a href="#M000395">call</a>
<a href="#M000393">map</a>
<a href="#M000388">new</a>
<a href="#M000387">new_from_string</a>
<a href="#M000386">parse_file</a>
<a href="#M000391">run</a>
<a href="#M000394">to_app</a>
<a href="#M000390">use</a>
<a href="#M000392">warmup</a>
</div>
</div>
</div>
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<div id="methods">
<h3 class="section-bar">Public Class methods</h3>
<div id="method-M000389" class="method-detail">
<a name="M000389"></a>
<div class="method-heading">
<a href="Builder.src/M000389.html" target="Code" class="method-signature"
onclick="popupCode('Builder.src/M000389.html');return false;">
<span class="method-name">app</span><span class="method-args">(default_app = nil, &block)</span>
</a>
</div>
<div class="method-description">
</div>
</div>
<div id="method-M000388" class="method-detail">
<a name="M000388"></a>
<div class="method-heading">
<a href="Builder.src/M000388.html" target="Code" class="method-signature"
onclick="popupCode('Builder.src/M000388.html');return false;">
<span class="method-name">new</span><span class="method-args">(default_app = nil,&block)</span>
</a>
</div>
<div class="method-description">
</div>
</div>
<div id="method-M000387" class="method-detail">
<a name="M000387"></a>
<div class="method-heading">
<a href="Builder.src/M000387.html" target="Code" class="method-signature"
onclick="popupCode('Builder.src/M000387.html');return false;">
<span class="method-name">new_from_string</span><span class="method-args">(builder_script, file="(rackup)")</span>
</a>
</div>
<div class="method-description">
</div>
</div>
<div id="method-M000386" class="method-detail">
<a name="M000386"></a>
<div class="method-heading">
<a href="Builder.src/M000386.html" target="Code" class="method-signature"
onclick="popupCode('Builder.src/M000386.html');return false;">
<span class="method-name">parse_file</span><span class="method-args">(config, opts = Server::Options.new)</span>
</a>
</div>
<div class="method-description">
</div>
</div>
<h3 class="section-bar">Public Instance methods</h3>
<div id="method-M000395" class="method-detail">
<a name="M000395"></a>
<div class="method-heading">
<a href="Builder.src/M000395.html" target="Code" class="method-signature"
onclick="popupCode('Builder.src/M000395.html');return false;">
<span class="method-name">call</span><span class="method-args">(env)</span>
</a>
</div>
<div class="method-description">
</div>
</div>
<div id="method-M000393" class="method-detail">
<a name="M000393"></a>
<div class="method-heading">
<a href="Builder.src/M000393.html" target="Code" class="method-signature"
onclick="popupCode('Builder.src/M000393.html');return false;">
<span class="method-name">map</span><span class="method-args">(path, &block)</span>
</a>
</div>
<div class="method-description">
<p>
Creates a route within the application.
</p>
<pre>
Rack::Builder.app do
map '/' do
run Heartbeat
end
end
</pre>
<p>
The <tt><a href="Builder.html#M000390">use</a></tt> method can also be used
here to specify middleware to <a href="Builder.html#M000391">run</a> under
a specific path:
</p>
<pre>
Rack::Builder.app do
map '/' do
use Middleware
run Heartbeat
end
end
</pre>
<p>
This example includes a piece of middleware which will <a
href="Builder.html#M000391">run</a> before requests hit <tt>Heartbeat</tt>.
</p>
</div>
</div>
<div id="method-M000391" class="method-detail">
<a name="M000391"></a>
<div class="method-heading">
<a href="Builder.src/M000391.html" target="Code" class="method-signature"
onclick="popupCode('Builder.src/M000391.html');return false;">
<span class="method-name">run</span><span class="method-args">(app)</span>
</a>
</div>
<div class="method-description">
<p>
Takes an argument that is an object that responds to <a
href="Builder.html#M000395">call</a> and returns a <a
href="../Rack.html">Rack</a> response. The simplest form of this is a
lambda object:
</p>
<pre>
run lambda { |env| [200, { "Content-Type" => "text/plain" }, ["OK"]] }
</pre>
<p>
However this could also be a class:
</p>
<pre>
class Heartbeat
def self.call(env)
[200, { "Content-Type" => "text/plain" }, ["OK"]]
end
end
run Heartbeat
</pre>
</div>
</div>
<div id="method-M000394" class="method-detail">
<a name="M000394"></a>
<div class="method-heading">
<a href="Builder.src/M000394.html" target="Code" class="method-signature"
onclick="popupCode('Builder.src/M000394.html');return false;">
<span class="method-name">to_app</span><span class="method-args">()</span>
</a>
</div>
<div class="method-description">
</div>
</div>
<div id="method-M000390" class="method-detail">
<a name="M000390"></a>
<div class="method-heading">
<a href="Builder.src/M000390.html" target="Code" class="method-signature"
onclick="popupCode('Builder.src/M000390.html');return false;">
<span class="method-name">use</span><span class="method-args">(middleware, *args, &block)</span>
</a>
</div>
<div class="method-description">
<p>
Specifies middleware to <a href="Builder.html#M000390">use</a> in a stack.
</p>
<pre>
class Middleware
def initialize(app)
@app = app
end
def call(env)
env["rack.some_header"] = "setting an example"
@app.call(env)
end
end
use Middleware
run lambda { |env| [200, { "Content-Type" => "text/plain" }, ["OK"]] }
</pre>
<p>
All requests through to this application will first be processed by the
middleware class. The <tt><a href="Builder.html#M000395">call</a></tt>
method in this example sets an additional environment key which then can be
referenced in the application if required.
</p>
</div>
</div>
<div id="method-M000392" class="method-detail">
<a name="M000392"></a>
<div class="method-heading">
<a href="Builder.src/M000392.html" target="Code" class="method-signature"
onclick="popupCode('Builder.src/M000392.html');return false;">
<span class="method-name">warmup</span><span class="method-args">(prc=nil, &block)</span>
</a>
</div>
<div class="method-description">
<p>
Takes a lambda or block that is used to warm-up the application.
</p>
<pre>
warmup do |app|
client = Rack::MockRequest.new(app)
client.get('/')
end
use SomeMiddleware
run MyApp
</pre>
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