From: "Peña, Botp" <botp@...>
Date: 2008-08-20T11:50:43+09:00
Subject: Re: define_method issue

From: Raj Singh [mailto:neeraj.jsr@gmail.com] 
# Based on the following example should I conclude whether I use
# instance_eval or class_eval, define_method always creates an instance
# method....

Hi Raj,
you may need to access Music's meta/eigenclass in order to define a singleton for it.

eg, in ruby 1.8.6 latest stable

irb(main):044:0> def add_class_method(c, m, &b)
irb(main):045:1>   eigenclass = class << c; self; end
irb(main):046:1>   eigenclass.class_eval {
irb(main):047:2*     define_method(m, &b)
irb(main):048:2>   }
irb(main):049:1> end
=> nil
irb(main):050:0>
irb(main):051:0* add_class_method(Music, :rock2) do
irb(main):052:1*     puts 'i am a rock, too :)'
irb(main):053:1> end
=> #<Proc:0x028c6c00@(irb):51>
irb(main):054:0> Music.rock2
i am a rock, too :)
=> nil
irb(main):056:0>  [RUBY_VERSION,RUBY_PATCHLEVEL,RUBY_RELEASE_DATE, RUBY_PLATFORM
]
=> ["1.8.6", 286, "2008-08-08", "i386-mswin32"]


in 1.9, it is much simpler

irb(main):002:0> class Music
irb(main):003:1> end
=> nil
irb(main):004:0> Music.define_singleton_method(:rock) do
irb(main):005:1*   puts "i am a classy rock"
irb(main):006:1> end
=> #<Proc:0xe033dc@(irb):5 (lambda)>
irb(main):007:0> Music.rock
i am a classy rock
=> nil
irb(main):008:0> RUBY_VERSION
=> "1.9.0"


kind regards -botp