From: Yukihiro Matsumoto <matz@...>
Date: 2006-09-26T07:50:04+09:00
Subject: Re: How to copy a method from one class to another

Hi,

In message "Re: How to copy a method from one class to another"
    on Tue, 26 Sep 2006 05:15:20 +0900, "Sam Kong" <sam.s.kong@gmail.com> writes:

|Mix-in is the right way in Ruby.
|However, for mix-in, all things should be designed before
|implementation.

If you are not allowed to modify existing classes.  Most of the cases
rewriting 

  class C1
    def f
      p self.class
    end
  end

to

  module M1
    def f
      p self.class
    end
  end

  class C1
    include M1
  end

  class C2
    include M1
  end

is trivial.  You don't need to design everything before
implementation, but just have to evolve classes.

If you are not allowed to modify pre-existing class, you need to use
some kind of delegation.

							matz.