From: Rick DeNatale <rick.denatale@...>
Date: 2009-09-01T07:11:17+09:00
Subject: [ruby-core:25237] Re: Module#prepend and Array#prepend

On Mon, Aug 31, 2009 at 2:24 PM, Yusuke ENDOH<mame@tsg.ne.jp> wrote:
> Hi,
>
> 2009/9/1 Carl Lerche <clerche@engineyard.com>:

>
>> This causes pain when you are using a ruby library that does not
>> assume that you will be extending classes. Rails "solved" this problem using
>> alias_method_chain, but this method can cause confusion.
>
...
>
> Then, I guess that what we really need is a method wrapping feature:
>
> �class Person
> � �refine_method(:speak) do |old_method, words|
> � � �# old_method is a Method of original definition
> � � �old_method.call("#{ words }!")
> � �end
> �end
> �Person.new.speak("matz") #=> "matz!"

Yusuke-san,

Are you familiar with alias_method_chain in Rails which Carl mentioned.

This is a common rails extension idiom which you'd use like this

module Exclaimer
   def speak_with_exclaimer(words)
        speak_with_exclaimer("#{words}!")
   end

   def.self.included(base)
       base.alias_method_chain :speak, :exclaimer
   end
end

and alias_method_chain aliases the existing speak method to
send_without_exclaimer, and then the speak_with_exclaimer method to
speak

This allows independently developed class extension modules to be
composed, but it can be a bit confusing at times, particularly when
debugging because of the aliasing.


-- 
Rick DeNatale

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