From: Gavin Kistner <gavin.kistner@...>
Date: 2006-09-26T01:43:52+09:00
Subject: Re: How to copy a method from one class to another

From: Sam Kong [mailto:sam.s.kong@gmail.com] 
> Now I want C2 to have f method so that I can call C2.new.f.

Select lines 2-4.
Copy.
Move caret inside C2.
Paste.

:)

Ruby's methods are not first-class functions like Lua or JavaScript
have. Other, first-class functions exist (procs/lambdas), but Methods
are not these.

Others have given you good suggestions (modules, inheritance). I think
the most important advice is to describe what you want to do instead of
how you think you might want to accomplish it. :)



Here's one other technique, that very likely is too complicated and
isn't what you wanted. It gives C2 access to the proc defined at the
class level of C1, which it can invoke on itself.

Of course, any methods you try to invoke on 'self' inside that proc must
exist both for the C1 and the C2 instance...in which case, you probably
wanted inheritance or module inclusion anyhow.

class C1
  class << self
    attr_reader :complex_stuff
  end
  @complex_stuff = lambda{
    puts "My encoded representation is #{self.inspect.reverse}"
  }
  
  def initialize( name )
    @name = name
  end

  def do_complex_stuff
    self.instance_eval( &self.class.complex_stuff )
  end
end
    
C1.new( 'charlie' ).do_complex_stuff
#=> My encoded representation is >"eilrahc"=eman@ 8194382x0:1C<#

class C2
  def do_complex_stuff
    self.instance_eval( &C1.complex_stuff )
  end
end

C2.new.do_complex_stuff
#=> My encoded representation is >0714382x0:2C<#