Moduleのincludeとかextendとか

Moduleのincludeとextendまわりの自分用サンプル

基本

module Foo
  def self.included(base)
    base.extend ClassMethods
    base.__send__ :include, InstanceMethods
  end

  module ClassMethods
    # クラスメソッドの定義
  end

  module InstanceMethods
    # インスタンスメソッドの定義
  end
end

(Bar = Class.new).__send__ :include, Foo

p Bar.ancestors
#=> [Bar, Foo::InstanceMethods, Foo, Object, Kernel]
p (class << Bar; self end).ancestors
#=> [Foo::ClassMethods, Class, Module, Object, Kernel]
p Bar.included_modules
#=> [Foo::InstanceMethods, Foo, Kernel]
p (class << Bar; self end).included_modules
#=> [Foo::ClassMethods, Kernel]

Module#extended, Module#included

module SuperModule
  module ModuleMethods
    def self.extended(base)
      puts "#{self} was extended by #{base}"
    end
  end
  extend ModuleMethods

  module InstanceMethods
    def self.included(base)
      puts "#{self} was included by #{base}"
    end
  end
  include InstanceMethods
end
#=> SuperModule::ModuleMethods was extended by SuperModule
#=> SuperModule::InstanceMethods was included by SuperModule

Rails pluginなど

(追記) class_eval撲滅

module UsefulModule
  def self.included(base)
    base.extend ClassMethods
  end

  module ClassMethods
    def activate_useful_module
        self.__send__ :include, UsefulModule::InstanceMethods
    end
  end

  module InstanceMethods
    # インスタンスメソッドの定義
  end
end
ExistingClass.__send__ :include, UsefulModule

# 時は流れて・・・
ExistingClass.activate_useful_module
#=> ExistingClassのインスタンスはUsefulModuleの協力なメソッド群を利用できるようになった

(追記)

禁じ手

module ForbiddenModule
  def self.included(base)
    base.__send__ :include, InstanceMethods
  end

  module InstanceMethods
    def self.included(mod)
      puts "#{self} was included by #{mod}"
      candidate =  instance_methods & mod.instance_methods(false)
      candidate.each do |method|
        mod.__send__ :remove_method, method
      end
    end

    # 強制的に上書きするインスタンスメソッドの定義
  end
end

VictimClass.__send__ :include, ForbiddenModule