メタプログラミングRuby勉強会

alias.rb

class MyClass
  def old_method
    "my_method"
  end

  alias new_method old_method
  # alias_method :new_method, :old_method
end

obj = MyClass.new
obj.old_method #=> "my_method"
obj.new_method #=> "my_method"

# アラウンドエイリアス

class MyClass
  def old_method
    warn "deprecated!"
    new_method
  end
end

obj = MyClass.new
obj.old_method #=> "my_method"
deprecated!
obj.new_method #=> "my_method"


# alias_method_chain pattern

class MyClass
  def new_method_with_warning
    warn "also deprecated!"
    new_method_without_warning
  end
  alias new_method_without_warning new_method
  alias new_method new_method_with_warning
  # alias_method_chain :new_method, :warning
end

obj = MyClass.new
obj.new_method #=> "my_method"
also deprecated!
obj.new_method_with_warning #=> "my_method"
also deprecated!
obj.new_method_without_warning #=> "my_method"

extend.rb

module MyModule1
  def my_method
    "hello"
  end
end

class MyClass0
  class << self
    include MyModule1
  end
end

class MyClass1
  extend MyModule1
end

# or ActiveSupport::Concern is easy

require 'active_support/concern'
module MyModule2
  extend ActiveSupport::Concern

  module ClassMethods
    def my_method
      "hello"
    end
  end
end

class MyClass2
  include MyModule2
end