vendor/rails/actionpack/lib/action_controller/vendor/rack-1.0/rack/builder.rb

   1 module Rack
   2   # Rack::Builder implements a small DSL to iteratively construct Rack
   3   # applications.
   4   #
   5   # Example:
   6   #
   7   #  app = Rack::Builder.new {
   8   #    use Rack::CommonLogger
   9   #    use Rack::ShowExceptions
  10   #    map "/lobster" do
  11   #      use Rack::Lint
  12   #      run Rack::Lobster.new
  13   #    end
  14   #  }
  15   #
  16   # Or
  17   #
  18   #  app = Rack::Builder.app do
  19   #    use Rack::CommonLogger
  20   #    lambda { |env| [200, {'Content-Type' => 'text/plain'}, 'OK'] }
  21   #  end
  22   #
  23   # +use+ adds a middleware to the stack, +run+ dispatches to an application.
  24   # You can use +map+ to construct a Rack::URLMap in a convenient way.
  25
  26   class Builder
  27     def initialize(&block)
  28       @ins = []
  29       instance_eval(&block) if block_given?
  30     end
  31
  32     def self.app(&block)
  33       self.new(&block).to_app
  34     end
  35
  36     def use(middleware, *args, &block)
  37       @ins << lambda { |app| middleware.new(app, *args, &block) }
  38     end
  39
  40     def run(app)
  41       @ins << app #lambda { |nothing| app }
  42     end
  43
  44     def map(path, &block)
  45       if @ins.last.kind_of? Hash
  46         @ins.last[path] = self.class.new(&block).to_app
  47       else
  48         @ins << {}
  49         map(path, &block)
  50       end
  51     end
  52
  53     def to_app
  54       @ins[-1] = Rack::URLMap.new(@ins.last)  if Hash === @ins.last
  55       inner_app = @ins.last
  56       @ins[0...-1].reverse.inject(inner_app) { |a, e| e.call(a) }
  57     end
  58
  59     def call(env)
  60       to_app.call(env)
  61     end
  62   end
  63 end