Callbacks in pure ruby

gistfile1.rb

module CallbackPureRuby
  def self.included(klass)
    klass.extend ClassMethods
    klass.initialize_included_features
  end

  module ClassMethods
    def initialize_included_features
      @callbacks = Hash[:before, {}, :after, {}]

      class << self
        attr_accessor :callbacks
        attr_accessor :setting_callback
      end
    end

    def store_callbacks(type, method_name, *callback_methods)
      callbacks[type][method_name] = callback_methods

      if !setting_callback
        prepend_method(method_name)
      end
    end

    def method_missing(method, *args, &block)
      if method.to_s =~ /^before|after$/
        store_callbacks(method, *args)
      else
        super
      end
    end

    def prepend_method(original_method)
      @setting_callback = true

      save_with_callbacks = Module.new do
        define_method(original_method) do |*args, &block|
          trigger_callbacks(original_method, :before)
          return_val = super()
          trigger_callbacks(original_method, :after)
          return_val
        end
      end

      prepend save_with_callbacks

      @setting_callback = false
    end
  end

  def trigger_callbacks(method_name, callback_type)
    unless self.class.callbacks[callback_type][method_name].nil?
      self.class.callbacks[callback_type][method_name].each{ |callback| __send__ callback }
    end
  end
end