rails/actionpack/lib/action_controller/mime_responds.rb

module ActionController #:nodoc:
  module MimeResponds #:nodoc:
    def self.included(base)
      base.send(:include, ActionController::MimeResponds::InstanceMethods)
    end

    module InstanceMethods
      def respond_to(&block)
        responder = Responder.new(block.binding)
        yield responder
        responder.respond
      end
    end
    
    class Responder #:nodoc:
      def initialize(block_binding)
        @block_binding = block_binding
        @mime_type_priority = eval("request.accepts", block_binding)
        @order     = []
        @responses = {}
      end
      
      for mime_type in %w( all html js xml rss atom yaml )
        eval <<-EOT
          def #{mime_type}(&block)
            @order << Mime::#{mime_type.upcase}
            @responses[Mime::#{mime_type.upcase}] = block
          end
        EOT
      end
      
      def respond
        for priority in @mime_type_priority
          if priority == Mime::ALL
            @responses[@order.first].call
            return
          else
            if @order.include?(priority)
              @responses[priority].call
              return # mime type match found, be happy and return
            end
          end
        end
        
        if @order.include?(Mime::ALL)
          @responses[Mime::ALL].call
        else
          eval 'render(:nothing => true, :status => "406 Not Acceptable")', @block_binding
        end
      end
    end
  end
end