08 - automatically initializing mixed-in modules.rb

O Reilly Ruby Cookbook source code

class Class
  def included_modules
    @included_modules ||= []
  end
  
  alias_method :old_new, :new
  def new(*args, &block)
    obj = old_new(*args, &block)
    self.included_modules.each do |mod|
      mod.initialize if mod.respond_to?(:initialize)
    end
    obj
  end
end
#---
module Initializable

  def self.included(mod)
    mod.extend ClassMethods
  end

  module ClassMethods
    def included(mod)
      if mod.class != Module  #in case Initializeable is mixed-into a class
        puts "Adding #{self} to #{mod}'s included_modules" if $DEBUG
        mod.included_modules << self
      end
    end
  end
end
#---
module A
  include Initializable
  def self.initialize
    puts "A's initialized."
  end
end

module B
  include Initializable
  def self.initialize
    puts "B's initialized."
  end
end
#---
class BothAAndB
  include A
  include B
end

both = BothAAndB.new
# A's initialized.
# B's initialized.
#---