= Sinatra

Sinatra is a DSL for quickly creating web applications in Ruby with minimal
effort:

  # myapp.rb
  require 'sinatra'
  
  get '/' do
    'Hello world!'
  end

Install the gem and run with:

  gem install sinatra
  ruby -rubygems myapp.rb

View at: http://localhost:4567

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

== Routes

In Sinatra, a route is an HTTP method paired with an URL matching pattern.
Each route is associated with a block:

  get '/' do
    .. show something ..
  end

  post '/' do
    .. create something ..
  end

  put '/' do
    .. update something ..
  end

  delete '/' do
    .. annihilate something ..
  end
  
  options '/' do
    .. appease something ..
  end

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

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

  get '/hello/:name' do
    # matches "GET /hello/foo" and "GET /hello/bar"
    # params[:name] is 'foo' or 'bar'
    "Hello #{params[:name]}!"
  end

You can also access named parameters via block parameters:

  get '/hello/:name' do |n|
    "Hello #{n}!"
  end

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

  get '/say/*/to/*' do
    # matches /say/hello/to/world
    params[:splat] # => ["hello", "world"]
  end

  get '/download/*.*' do
    # matches /download/path/to/file.xml
    params[:splat] # => ["path/to/file", "xml"]
  end

Route matching with Regular Expressions:

  get %r{/hello/([\w]+)} do
    "Hello, #{params[:captures].first}!"
  end

Or with a block parameter:

  get %r{/hello/([\w]+)} do |c|
    "Hello, #{c}!"
  end

=== Conditions

Routes may include a variety of matching conditions, such as the user agent:

  get '/foo', :agent => /Songbird (\d\.\d)[\d\/]*?/ do
    "You're using Songbird version #{params[:agent][0]}"
  end

  get '/foo' do
    # Matches non-songbird browsers
  end

Other available conditions are +host_name+ and +provides+:

  get '/', :host_name => /^admin\./ do
    "Admin Area, Access denied!"
  end

  get '/', :provides => 'html' do
    haml :index
  end
  
  get '/', :provides => ['rss', 'atom', 'xml'] do
    builder :feed
  end

You can easily define your own conditions:

  set(:probability) { |value| condition { rand <= value } }
  
  get '/win_a_car', :probability => 0.1 do
    "You won!"
  end
  
  get '/win_a_car' do
    "Sorry, you lost."
  end

=== Return Values

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.

You can return any object that would either be a valid Rack response, Rack
body object or HTTP status code:

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

That way we can for instance easily implement a streaming example:

    class Stream
      def each
        100.times { |i| yield "#{i}\n" }
      end
    end

    get('/') { Stream.new }

== Static Files

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

  set :public, File.dirname(__FILE__) + '/static'

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

== Views / Templates

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

  set :views, File.dirname(__FILE__) + '/templates'

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 <tt>:'subdir/template'</tt>). You must use a symbol because 
otherwise rendering methods will render any strings passed to them 
directly.

=== Haml Templates

The <tt>haml</tt> gem/library is required to render HAML templates:

  # You'll need to require haml in your app
  require 'haml'

  get '/' do
    haml :index
  end

Renders <tt>./views/index.haml</tt>.

{Haml's options}[http://haml-lang.com/docs/yardoc/file.HAML_REFERENCE.html#options]
can be set globally through Sinatra's configurations,
see {Options and Configurations}[http://www.sinatrarb.com/configuration.html],
and overridden on an individual basis.

  set :haml, :format => :html5 # default Haml format is :xhtml

  get '/' do
    haml :index, :format => :html4 # overridden
  end


=== Erb Templates

  # You'll need to require erb in your app
  require 'erb'

  get '/' do
    erb :index
  end

Renders <tt>./views/index.erb</tt>.

=== Erubis Templates

The <tt>erubis</tt> gem/library is required to render Erubis templates:

  # You'll need to require erubis in your app
  require 'erubis'

  get '/' do
    erubis :index
  end

Renders <tt>./views/index.erubis</tt>.

It is also possible to replace Erb with Erubis:

  require 'erubis'
  Tilt.register :erb, Tilt[:erubis]
  
  get '/' do
    erb :index
  end

Renders <tt>./views/index.erb</tt> with Erubis.

=== Builder Templates

The <tt>builder</tt> gem/library is required to render builder templates:

  # You'll need to require builder in your app
  require 'builder'

  get '/' do
    builder :index
  end

Renders <tt>./views/index.builder</tt>.

=== Nokogiri Templates

The <tt>nokogiri</tt> gem/library is required to render nokogiri templates:

  # You'll need to require nokogiri in your app
  require 'nokogiri'

  get '/' do
    nokogiri :index
  end

Renders <tt>./views/index.nokogiri</tt>.

=== Sass Templates

The <tt>haml</tt> or <tt>sass</tt> gem/library is required to render Sass templates:

  # You'll need to require haml or sass in your app
  require 'sass'

  get '/stylesheet.css' do
    sass :stylesheet
  end

Renders <tt>./views/stylesheet.sass</tt>.

{Sass' options}[http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html#options]
can be set globally through Sinatra's configurations,
see {Options and Configurations}[http://www.sinatrarb.com/configuration.html],
and overridden on an individual basis.

  set :sass, :style => :compact # default Sass style is :nested

  get '/stylesheet.css' do
    sass :stylesheet, :style => :expanded # overridden
  end

=== Scss Templates

The <tt>haml</tt> or <tt>sass</tt> gem/library is required to render Scss templates:

  # You'll need to require haml or sass in your app
  require 'sass'

  get '/stylesheet.css' do
    scss :stylesheet
  end

Renders <tt>./views/stylesheet.scss</tt>.

{Scss' options}[http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html#options]
can be set globally through Sinatra's configurations,
see {Options and Configurations}[http://www.sinatrarb.com/configuration.html],
and overridden on an individual basis.

  set :scss, :style => :compact # default Scss style is :nested

  get '/stylesheet.css' do
    scss :stylesheet, :style => :expanded # overridden
  end

=== Less Templates

The <tt>less</tt> gem/library is required to render Less templates:

  # You'll need to require less in your app
  require 'less'

  get '/stylesheet.css' do
    less :stylesheet
  end

Renders <tt>./views/stylesheet.less</tt>.

=== Liquid Templates

The <tt>liquid</tt> gem/library is required to render Liquid templates:

  # You'll need to require liquid in your app
  require 'liquid'

  get '/' do
    liquid :index
  end

Renders <tt>./views/index.liquid</tt>.

Since you cannot call Ruby methods (except for +yield+) from a Liquid
template, you almost always want to pass locals to it:

  liquid :index, :locals => { :key => 'value' }

=== Markdown Templates

The <tt>rdiscount</tt> gem/library is required to render Markdown templates:

  # You'll need to require rdiscount in your app
  require "rdiscount"
  
  get '/' do
    markdown :index
  end

Renders <tt>./views/index.markdown</tt> (+md+ and +mkd+ are also valid file
extensions).

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:

  erb :overview, :locals => { :text => markdown(:introduction) }

Note that you may also call the +markdown+ method from within other templates:

  %h1 Hello From Haml!
  %p= markdown(:greetings)

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 <tt>:layout_engine</tt> option:

  get '/' do
    markdown :index, :layout_engine => :erb
  end

This will render <tt>./views/index.md</tt> with <tt>./views/layout.erb</tt> as
layout.

Remember that you can set such rendering options globally:

  set :markdown, :layout_engine => :haml, :layout => :post

  get '/' do
    markdown :index
  end

This will render <tt>./views/index.md</tt> (and any other Markdown template)
with <tt>./views/post.haml</tt> as layout.

It is also possible to parse Markdown with BlueCloth rather than RDiscount:

  require 'bluecloth'
  
  Tilt.register 'markdown', BlueClothTemplate
  Tilt.register 'mkd',      BlueClothTemplate
  Tilt.register 'md',       BlueClothTemplate
  
  get '/' do
    markdown :index
  end

Renders <tt>./views/index.md</tt> with BlueCloth.

=== Textile Templates

The <tt>RedCloth</tt> gem/library is required to render Textile templates:

  # You'll need to require redcloth in your app
  require "redcloth"

  get '/' do
    textile :index
  end

Renders <tt>./views/index.textile</tt>.

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

  erb :overview, :locals => { :text => textile(:introduction) }

Note that you may also call the +textile+ method from within other templates:

  %h1 Hello From Haml!
  %p= textile(:greetings)

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

  get '/' do
    textile :index, :layout_engine => :erb
  end

This will render <tt>./views/index.textile</tt> with
<tt>./views/layout.erb</tt> as layout.

Remember that you can set such rendering options globally:

  set :textile, :layout_engine => :haml, :layout => :post

  get '/' do
    textile :index
  end

This will render <tt>./views/index.textile</tt> (and any other Textile
template) with <tt>./views/post.haml</tt> as layout.

=== RDoc Templates

The <tt>rdoc</tt> gem/library is required to render RDoc templates:

  # You'll need to require rdoc in your app
  require "rdoc"

  get '/' do
    rdoc :index
  end

Renders <tt>./views/index.rdoc</tt>.

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:

  erb :overview, :locals => { :text => rdoc(:introduction) }

Note that you may also call the +rdoc+ method from within other templates:

  %h1 Hello From Haml!
  %p= rdoc(:greetings)

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 <tt>:layout_engine</tt> option:

  get '/' do
    rdoc :index, :layout_engine => :erb
  end

This will render <tt>./views/index.rdoc</tt> with <tt>./views/layout.erb</tt> as
layout.

Remember that you can set such rendering options globally:

  set :rdoc, :layout_engine => :haml, :layout => :post

  get '/' do
    rdoc :index
  end

This will render <tt>./views/index.rdoc</tt> (and any other RDoc template)
with <tt>./views/post.haml</tt> as layout.

=== Radius Templates

The <tt>radius</tt> gem/library is required to render Radius templates:

  # You'll need to require radius in your app
  require 'radius'

  get '/' do
    radius :index
  end

Renders <tt>./views/index.radius</tt>.

Since you cannot call Ruby methods (except for +yield+) from a Radius
template, you almost always want to pass locals to it:

  radius :index, :locals => { :key => 'value' }

=== Markaby Templates

The <tt>markaby</tt> gem/library is required to render Markaby templates:

  # You'll need to require markaby in your app
  require 'markaby'

  get '/' do
    markaby :index
  end

Renders <tt>./views/index.mab</tt>.

You may also use inline Markaby:

  get '/' do
    markaby { h1 "Welcome!" }
  end

=== Slim Templates

The <tt>slim</tt> gem/library is required to render Slim templates:

  # You'll need to require slim in your app
  require 'slim'

  get '/' do
    slim :index
  end

Renders <tt>./views/index.slim</tt>.

=== CoffeeScript Templates

The <tt>coffee-script</tt> gem/library and at least <b>one</b> of the
following options to execute JavaScript:

* +node+ (from Node.js) in your path
* you must be running on OSX
* +therubyracer+ gem/library

See http://github.com/josh/ruby-coffee-script for an updated list of options.

Now you can render CoffeeScript templates:

  # You'll need to require coffee-script in your app
  require 'coffee-script'

  get '/application.js' do
    coffee :application
  end

Renders <tt>./views/application.coffee</tt>.

=== Embedded Templates

  get '/' do
    haml '%div.title Hello World'
  end

Renders the embedded template string.

=== Accessing Variables in Templates

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

  get '/:id' do
    @foo = Foo.find(params[:id])
    haml '%h1= @foo.name'
  end

Or, specify an explicit Hash of local variables:

  get '/:id' do
    foo = Foo.find(params[:id])
    haml '%h1= foo.name', :locals => { :foo => foo }
  end

This is typically used when rendering templates as partials from within
other templates.

=== Inline Templates

Templates may be defined at the end of the source file:

  require 'sinatra'

  get '/' do
    haml :index
  end

  __END__

  @@ layout
  %html
    = yield

  @@ index
  %div.title Hello world!!!!!

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

=== Named Templates

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

  template :layout do
    "%html\n  =yield\n"
  end

  template :index do
    '%div.title Hello World!'
  end

  get '/' do
    haml :index
  end

If a template named "layout" exists, it will be used each time a template
is rendered. You can individually disable layouts by passing <tt>:layout => false</tt>
or disable them by default via <tt>set :haml, :layout => false</tt>.

  get '/' do
    haml :index, :layout => !request.xhr?
  end

=== Associating File Extensions

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

  Tilt.register :tt, Tilt[:textile]

=== Adding Your Own Template Engine

First, register your engine with Tilt, then create a rendering method:

  Tilt.register :myat, MyAwesomeTemplateEngine

  helpers do
    def myat(*args) render(:myat, *args) end
  end

  get '/' do
    myat :index
  end

Renders <tt>./views/index.myat</tt>. See https://github.com/rtomayko/tilt to
learn more about Tilt.

== Filters

+before+ filters are evaluated before each request within the same 
context as the routes. They can modify the request and the response. Instance 
variables set in these filters are accessible by routes and templates:

  before do
    @note = 'Hi!'
    request.path_info = '/foo/bar/baz'
  end

  get '/foo/*' do
    @note #=> 'Hi!'
    params[:splat] #=> 'bar/baz'
  end

+after+ filters are evaluated after each request within the same context
and can also modify the request and the response. Instance variables set in 
+before+ filters and routes are accessible by +after+ filters:

  after do
    puts response.status
  end

Note: Unless you use the +body+ 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.

Filters optionally taking a pattern will cause them to be evaluated only if 
the request path matches the pattern:

  before '/protected/*' do
    authenticate!
  end

  after '/create/:slug' do |slug|
    session[:last_slug] = slug
  end

Like routes, filters may also take conditions:

  before :agent => /Songbird/ do
    # ...
  end
  
  after '/blog/*', :host_name => 'example.com' do
    # ...
  end

== Helpers

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

  helpers do
    def bar(name)
      "#{name}bar"
    end
  end

  get '/:name' do
    bar(params[:name])
  end

=== Using Sessions

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

  enable :sessions

  get '/' do
    "value = " << session[:value].inspect
  end

  get '/:value' do
    session[:value] = params[:value]
  end

Note that <tt>enable :sessions</tt> 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, do *not* call <tt>enable :sessions</tt>, but instead pull in your
middleware of choice how you would any other middleware:

  use Rack::Session::Pool, :expire_after => 2592000

  get '/' do
    "value = " << session[:value].inspect
  end

  get '/:value' do
    session[:value] = params[:value]
  end

=== Halting

To immediately stop a request within a filter or route use:

  halt

You can also specify the status when halting:

  halt 410

Or the body:

  halt 'this will be the body'

Or both:

  halt 401, 'go away!'

With headers:

  halt 402, {'Content-Type' => 'text/plain'}, 'revenge'

=== Passing

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

  get '/guess/:who' do
    pass unless params[:who] == 'Frank'
    'You got me!'
  end

  get '/guess/*' do
    'You missed!'
  end

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

=== Triggering Another Route

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

  get '/foo' do
    status, headers, body = call request.env.merge("PATH_INFO" => '/bar')
    [status, body.upcase]
  end

  get '/bar' do
    "bar"
  end

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

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

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

=== Setting Body, Status Code and Headers

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
+body+ helper method. If you do so, you can use that method from there on to
access the body:

  get '/foo' do
    body "bar"
  end
  
  after do
    puts body
  end

It is also possible to pass a block to +body+, that will be executed by the Rack
handler (this can be used to implement streaming, see "Return Values").

Similar to +body+, you can also set the status code and headers:

  get '/foo' do
    status 418
    headers \
      "Allow"   => "BREW, POST, GET, PROPFIND, WHEN"
      "Refresh" => "Refresh: 20; http://www.ietf.org/rfc/rfc2324.txt"
    body "I'm a tea pot!"
  end

Like +body+, +headers+ and +status+ with no arguments can be used to access
their current values.

=== Mime Types

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

  mime_type :foo, 'text/foo'

You can also use it with the +content_type+ helper:

  get '/' do
    content_type :foo
    "foo foo foo"
  end

=== Generating URLs

For generating URLs you should use the +url+ helper method, for instance, in
Haml:

  %a{:href => url('/foo')} foo

It takes reverse proxies and Rack routers into account, if present.

This method is also aliased to +to+ (see below) for an
example).

=== Browser Redirect

You can trigger a browser redirect with the +redirect+ helper method:

  get '/foo' do
    redirect to('/bar')
  end

Any additional parameters are handled like arguments passed to +halt+:

  redirect to('/bar'), 303
  redirect 'http://google.com', 'wrong place, buddy'

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

  get '/foo' do
    "<a href='/bar'>do something</a>"
  end

  get '/bar' do
    do_something
    redirect back
  end

To pass arguments with a redirect, either add them to the query:

  redirect to('/bar?sum=42')

Or use a session:

  enable :session
  
  get '/foo' do
    session[:secret] = 'foo'
    redirect to('/bar')
  end
  
  get '/bar' do
    session[:secret]
  end

=== Cache Control

Setting your headers correctly is the foundation for proper HTTP caching.

You can easily set the Cache-Control header with like this:

  get '/' do
    cache_control :public
    "cache it!"
  end

Pro tip: Set up caching in a before filter.

  before do
    cache_control :public, :must_revalidate, :max_age => 60
  end

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

  before do
    expires 500, :public, :must_revalidate
  end

To properly use caches, you should consider using +etag+ and +last_modified+.
It is recommended to call those helpers *before* doing heavy lifting, as they
will immediately flush a response if the client already has the current
version in its cache.

  get '/article/:id' do
    @article = Article.find params[:id]
    last_modified @article.updated_at
    etag @article.sha1
    erb :article
  end

It is also possible to use a
{weak ETag}[http://en.wikipedia.org/wiki/HTTP_ETag#Strong_and_weak_validation]:

  etag @article.sha1, :weak

=== Sending Files

For sending files, you can use the <tt>send_file</tt> helper method:

  get '/' do
    send_file 'foo.png'
  end

It also takes a couple of options:

  send_file 'foo.png', :type => :jpg

The options are:

[filename]
  file name in response, defaults to the real file name.

[last_modified]
  value for Last-Modified header, defaults to the file's mtime.

[type]
  content type to use, guessed from the file extension if missing.

[disposition]
  used for Content-Disposition, possible values: +nil+ (default),
  <tt>:attachment</tt> and <tt>:inline</tt>

[length]
  Content-Length header, defaults to file size.

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.

=== Accessing the Request Object

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

  # app running on http://example.com/example
  get '/foo' do
    request.body              # request body sent by the client (see below)
    request.scheme            # "http"
    request.script_name       # "/example"
    request.path_info         # "/foo"
    request.port              # 80
    request.request_method    # "GET"
    request.query_string      # ""
    request.content_length    # length of request.body
    request.media_type        # media type of request.body
    request.host              # "example.com"
    request.get?              # true (similar methods for other verbs)
    request.form_data?        # false
    request["SOME_HEADER"]    # value of SOME_HEADER header
    request.referrer          # the referrer of the client or '/'
    request.user_agent        # user agent (used by :agent condition)
    request.cookies           # hash of browser cookies
    request.xhr?              # is this an ajax request?
    request.url               # "http://example.com/example/foo"
    request.path              # "/example/foo"
    request.ip                # client IP address
    request.secure?           # false (would be true over ssl)
    request.forwarded?        # true (if running behind a reverse proxy)
    request.env               # raw env hash handed in by Rack
  end

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

  before { request.path_info = "/" }
  
  get "/" do
    "all requests end up here"
  end

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

  post "/api" do
    request.body.rewind  # in case someone already read it
    data = JSON.parse request.body.read
    "Hello #{data['name']}!"
  end

=== Attachments

You can use the +attachment+ helper to tell the browser the response should be
stored on disk rather than displayed in the browser.

  get '/' do
    attachment
    "store it!"
  end

You can also pass it a file name:

  get '/' do
    attachment "info.txt"
    "store it!"
  end

=== Looking Up Template Files

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

  find_template settings.views, 'foo', Tilt[:haml] do |file|
    puts "could be #{file}"
  end

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:

  set :views, ['views', 'templates']

  helpers do
    def find_template(views, name, engine, &block)
      Array(views).each { |v| super(v, name, engine, &block) }
    end
  end

Another example would be to use different directories for different engines:

  set :views, :sass => 'views/sass', :haml => 'templates', :default => 'views'

  helpers do
    def find_template(views, name, engine, &block)
      _, folder = views.detect { |k,v| engine == Tilt[k] }
      folder ||= views[:default]
      super(folder, name, engine, &block)
    end
  end

You can also easily wrap this up in an extension and share with others!

Note that <tt>find_template</tt> 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 +render+ will use +break+ 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.

== Configuration

Run once, at startup, in any environment:

  configure do
    # setting one option
    set :option, 'value'
    
    # setting multiple options
    set :a => 1, :b => 2
    
    # same as `set :option, true`
    enable :option
    
    # same as `set :option, false`
    disable :option
    
    # you can also have dynamic settings with blocks
    set(:css_dir) { File.join(views, 'css') }
  end

Run only when the environment (RACK_ENV environment variable) is set to
<tt>:production</tt>:

  configure :production do
    ...
  end

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

  configure :production, :test do
    ...
  end

You can access those options via <tt>settings</tt>:

  configure do
    set :foo, 'bar'
  end

  get '/' do
    settings.foo? # => true
    settings.foo  # => 'bar'
    ...
  end

=== Available Settings

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

[add_charsets]        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:
                      
                        settings.add_charsets << "application/foobar"

[app_file]            main application file, used to detect project root,
                      views and public folder and inline templates.

[bind]                IP address to bind to (default: 0.0.0.0).
                      Only used for built-in server.

[default_encoding]    encoding to assume if unknown
                      (defaults to <tt>"utf-8"</tt>).

[dump_errors]         display errors in the log.

[environment]         current environment, defaults to <tt>ENV['RACK_ENV']</tt>,
                      or <tt>"development"</tt> if not available.

[logging]             use the logger.

[lock]                Places a lock around every request, only running
                      processing on request per Ruby process concurrently.
                      
                      Enabled if your app is not thread-safe.
                      Disabled per default.

[method_override]     use <tt>_method</tt> magic to allow put/delete forms in
                      browsers that don't support it.

[port]                Port to listen on. Only used for built-in server.

[prefixed_redirects]  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 per default.

[public]              folder public files are served from

[reload_templates]    whether or not to reload templates between requests.
                      Enabled in development mode and on Ruby 1.8.6 (to
                      compensate a bug in Ruby causing a memory leak).

[root]                project root folder.

[raise_errors]        raise exceptions (will stop application).

[run]                 if enabled, Sinatra will handle starting the web server,
                      do not enable if using rackup or other means.

[running]             is the built-in server running now?
                      do not change this setting!

[server]              server or list of servers to use for built-in server.
                      defaults to ['thin', 'mongrel', 'webrick'], order indicates
                      priority.

[sessions]            enable cookie based sessions.

[show_exceptions]     show a stack trace in the browser.

[static]              Whether Sinatra should handle serving static files.
                      Disable when using a Server able to do this on its own.
                      Disabling will boost performance.
                      Enabled per default.

[views]               views folder.

== Error Handling

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

=== Not Found

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

  not_found do
    'This is nowhere to be found.'
  end

=== Error

The +error+ handler is invoked any time an exception is raised from a route
block or a filter. The exception object can be obtained from the
<tt>sinatra.error</tt> Rack variable:

  error do
    'Sorry there was a nasty error - ' + env['sinatra.error'].name
  end

Custom errors:

  error MyCustomError do
    'So what happened was...' + request.env['sinatra.error'].message
  end

Then, if this happens:

  get '/' do
    raise MyCustomError, 'something bad'
  end

You get this:

  So what happened was... something bad

Alternatively, you can install an error handler for a status code:

  error 403 do
    'Access forbidden'
  end

  get '/secret' do
    403
  end

Or a range:

  error 400..510 do
    'Boom'
  end

Sinatra installs special <tt>not_found</tt> and <tt>error</tt> handlers when
running under the development environment.

== Rack Middleware

Sinatra rides on Rack[http://rack.rubyforge.org/], 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.

Sinatra makes building Rack middleware pipelines a cinch via a top-level
+use+ method:

  require 'sinatra'
  require 'my_custom_middleware'

  use Rack::Lint
  use MyCustomMiddleware

  get '/hello' do
    'Hello World'
  end

The semantics of +use+ are identical to those defined for the
Rack::Builder[http://rack.rubyforge.org/doc/classes/Rack/Builder.html] DSL
(most frequently used from rackup files). For example, the +use+ method
accepts multiple/variable args as well as blocks:

  use Rack::Auth::Basic do |username, password|
    username == 'admin' && password == 'secret'
  end

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

== Testing

Sinatra tests can be written using any Rack-based testing library
or framework. {Rack::Test}[http://gitrdoc.com/brynary/rack-test] is
recommended:

  require 'my_sinatra_app'
  require 'test/unit'
  require 'rack/test'

  class MyAppTest < Test::Unit::TestCase
    include Rack::Test::Methods

    def app
      Sinatra::Application
    end

    def test_my_default
      get '/'
      assert_equal 'Hello World!', last_response.body
    end

    def test_with_params
      get '/meet', :name => 'Frank'
      assert_equal 'Hello Frank!', last_response.body
    end

    def test_with_rack_env
      get '/', {}, 'HTTP_USER_AGENT' => 'Songbird'
      assert_equal "You're using Songbird!", last_response.body
    end
  end

NOTE: The built-in Sinatra::Test module and Sinatra::TestHarness class
are deprecated as of the 0.9.2 release.

== Sinatra::Base - Middleware, Libraries, and Modular Apps

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 DSL pollutes the Object namespace
and assumes a micro-app style configuration (e.g., a single application
file, ./public and ./views directories, logging, exception detail page,
etc.). That's where Sinatra::Base comes into play:

  require 'sinatra/base'

  class MyApp < Sinatra::Base
    set :sessions, true
    set :foo, 'bar'

    get '/' do
      'Hello world!'
    end
  end

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

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

<tt>Sinatra::Base</tt> is a blank slate. Most options are disabled by default,
including the built-in server. See {Options and Configuration}[http://sinatra.github.com/configuration.html]
for details on available options and their behavior.

=== Modular vs. Classic Style

Contrary to common believes, there is nothing wrong with classic style. If it
suits your application, you do not have to switch to a modular application.

There are only two downsides compared to modular style:

* You may only have one Sinatra application per Ruby process - if you plan to
  use more, switch to modular style.

* Classic style pollutes Object with delegator methods - if you plan to ship
  your application in a library/gem, switch to modular style.

There is no reason you cannot mix modular and classic style.

If switching from one style to the other, you should be aware of slight
differences in the setting:

  Setting             Classic                 Modular

  app_file            file loading sinatra    nil
  run                 $0 == app_file          false
  logging             true                    false
  method_override     true                    false
  inline_templates    true                    false


=== Serving a Modular Application

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

  # my_app.rb
  require 'sinatra/base'
  
  class MyApp < Sinatra::Base
    # ... app code here ...
    
    # start the server if ruby file is executed directly
    run! if app_file == $0
  end

Start with:

  ruby my_app.rb

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

  # config.ru
  require 'my_app'
  run MyApp

Run:

  rackup -p 4567

=== Using a Classic Style Application with a config.ru

Write your app file:

  # app.rb
  require 'sinatra'
  
  get '/' do
    'Hello world!'
  end

And a corresponding <tt>config.ru</tt>:

  require 'app'
  run Sinatra::Application

=== When to use a config.ru?

Good signs you probably want to use a <tt>config.ru</tt>:

* You want to deploy with a different Rack handler (Passenger, Unicorn,
  Heroku, ...).
* You want to use more than one subclass of <tt>Sinatra::Base</tt>.
* You want to use Sinatra only for middleware, but not as endpoint.

<b>There is no need to switch to a <tt>config.ru</tt> only because you
switched to modular style, and you don't have to use modular style for running
with a <tt>config.ru</tt>.</b>

=== Using Sinatra as Middleware

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/Ramaze/Camping/...).

  require 'sinatra/base'
  
  class LoginScreen < Sinatra::Base
    enable :sessions
    
    get('/login') { haml :login }
    
    post('/login') do
      if params[:name] = 'admin' and params[:password] = 'admin'
        session['user_name'] = params[:name]
      else
        redirect '/login'
      end
    end
  end
  
  class MyApp < Sinatra::Base
    # middleware will run before filters
    use LoginScreen
    
    before do
      unless session['user_name']
        halt "Access denied, please <a href='/login'>login</a>."
      end
    end
    
    get('/') { "Hello #{session['user_name']}." }
  end

== Scopes and Binding

The scope you are currently in determines what methods and variables are
available.

=== Application/Class Scope

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

Options created via +set+ are methods at class level:

    class MyApp < Sinatra::Base
      # Hey, I'm in the application scope!
      set :foo, 42
      foo # => 42
      
      get '/foo' do
        # Hey, I'm no longer in the application scope!
      end
    end

You have the application scope binding inside:

* Your application class body
* Methods defined by extensions
* The block passed to +helpers+
* Procs/blocks used as value for +set+

You can reach the scope object (the class) like this:

* Via the object passed to configure blocks (<tt>configure { |c| ... }</tt>)
* +settings+ from within request scope

=== Request/Instance Scope

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 +request+ and +session+ object or call rendering methods like
+erb+ or +haml+. You can access the application scope from within the request
scope via the +settings+ helper:

  class MyApp < Sinatra::Base
    # Hey, I'm in the application scope!
    get '/define_route/:name' do
      # Request scope for '/define_route/:name'
      @value = 42
      
      settings.get("/#{params[:name]}") do
        # Request scope for "/#{params[:name]}"
        @value # => nil (not the same request)
      end
      
      "Route defined!"
    end
  end

You have the request scope binding inside:

* get/head/post/put/delete/options blocks
* before/after filters
* helper methods
* templates/views

=== Delegation Scope

The delegation scope just forwards methods to the class scope. However, it
does not behave 100% 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
+self+). You can explicitly add method delegations by calling
<tt>Sinatra::Delegator.delegate :method_name</tt>.

You have the delegate scope binding inside:

* The top level binding, if you did <tt>require "sinatra"</tt>
* An object extended with the <tt>Sinatra::Delegator</tt> mixin

Have a look at the code for yourself: here's the
{Sinatra::Delegator mixin}[http://github.com/sinatra/sinatra/blob/ceac46f0bc129a6e994a06100aa854f606fe5992/lib/sinatra/base.rb#L1128]
being {included into the main namespace}[http://github.com/sinatra/sinatra/blob/ceac46f0bc129a6e994a06100aa854f606fe5992/lib/sinatra/main.rb#L28].

== Command Line

Sinatra applications can be run directly:

  ruby myapp.rb [-h] [-x] [-e ENVIRONMENT] [-p PORT] [-o HOST] [-s HANDLER]

Options are:

  -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 thin)
  -x # turn on the mutex lock (default is off)

== The Bleeding Edge
If you would like to use Sinatra's latest bleeding code, feel free to run your
application against the master branch, it should be rather stable.

We also push out prerelease gems from time to time, so you can do a

  gem install sinatra --pre

To get some of the latest features.

=== With Bundler
If you want to run your application with the latest Sinatra, using
{Bundler}[http://gembundler.com/] is the recommended way.

First, install bundler, if you haven't yet:

  gem install bundler

Then, in your project directory, create a +Gemfile+:

  source :rubygems
  gem 'sinatra', :git => "git://github.com/sinatra/sinatra.git"
  
  # other dependencies
  gem 'haml'                    # for instance, if you use haml
  gem 'activerecord', '~> 3.0'  # maybe you also need ActiveRecord 3.x

Note that you will have to list all your applications dependencies in there.
Sinatra's direct dependencies (Rack and Tilt) will however be automatically
fetched and added by Bundler.

Now you can run your app like this:

  bundle exec ruby myapp.rb

=== Roll Your Own
Create a local clone and run your app with the <tt>sinatra/lib</tt> directory
on the <tt>LOAD_PATH</tt>:

  cd myapp
  git clone git://github.com/sinatra/sinatra.git
  ruby -Isinatra/lib myapp.rb

To update the Sinatra sources in the future:

  cd myapp/sinatra
  git pull

=== Install Globally

You can build the gem on your own:

  git clone git://github.com/sinatra/sinatra.git
  cd sinatra
  rake sinatra.gemspec
  rake install

If you install gems as root, the last step should be

  sudo rake install

== Further Reading

* {Project Website}[http://www.sinatrarb.com/] - Additional documentation,
  news, and links to other resources.
* {Contributing}[http://www.sinatrarb.com/contributing] - Find a bug? Need
  help? Have a patch?
* {Issue tracker}[http://github.com/sinatra/sinatra/issues]
* {Twitter}[http://twitter.com/sinatra]
* {Mailing List}[http://groups.google.com/group/sinatrarb/topics]
* {IRC: #sinatra}[irc://chat.freenode.net/#sinatra] on http://freenode.net