array_object_webapp.rb

require 'rubygems' if RUBY_VERSION =~ /1\.8/
require 'rack'

require "#{File.dirname(__FILE__)}/webapp"

if __FILE__ == $0
  def usage
    STDERR.puts("Usage: #{$0} <webrick, thin, mongrel>")
    exit
  end

  def starting(app, server)
    STDOUT.puts("Starting: '#{app.inspect}' with '#{server}'")
  end

  usage if ARGV.empty?

  handler = ARGV.first
  app = [].to_web_app
  options = { :Port => 9292 }

  case handler
  when 'webrick'
    starting(app, 'webrick')
    Rack::Handler::WEBrick.run(app, options)
  when 'thin'
    starting(app, 'thin')
    Rack::Handler::Thin.run(app, options)
  when 'mongrel'
    starting(app, 'mongrel')
    Rack::Handler::Mongrel.run(app, options)
  else
    usage
  end
end

object_app.rb

module Rack
  # Turn any object into a Rack app.
  #
  #   class Array
  #     include Rack::ObjectApp
  #   end
  #
  #   run Array.new.to_rack_app
  module ObjectApp

    # Return +self+ as a Rack app.
    def to_rack_app
      class << self
        define_method(:call) do |env|
          func, *attrs = env['PATH_INFO'].split('/').reject(&:empty?)
          [ 200, { 'Content-Type' => 'text/html' }, send(func, *attrs) ]
        end
      end
      self
    end

  end
end

webapp.rb

require 'rubygems'
require 'rack'

class Object
  def webapp
    class << self
       define_method :call do |env|
         func, *attrs = env['PATH_INFO'].split('/').reject(&:empty?)
         [200, {}, send(func, *attrs)]
       end
    end
    self
  end
end

# Rack::Handler::Mongrel.run [].webapp, :Port => 9292
#                           ^^^^^^^^^^^
#                              |          (x)
#                         ROFLSCALE DB ---/
#


# http://localhost:9292/push/1  -> 1
# http://localhost:9292/push/2  -> 12
# http://localhost:9292/push/3  -> 123

# http://localhost:9292/to_a    -> 123

# http://localhost:9292/pop     -> 3
# http://localhost:9292/shift   -> 1