From: botp <botpena@...>
Date: 2010-10-07T09:52:04+09:00
Subject: Re: Why does Module#include exclude the module's metaclass?

On Thu, Oct 7, 2010 at 7:33 AM, John Mair <jrmair@gmail.com> wrote:
> When classes are inherited in Ruby the singleton classes are also
> inherited:
>
> class A
>  def self.hello
>    puts "hello"
>  end
> end
>
> class B < A
> end
>
> B.hello #=> "hello"

ok. single inheritance

> Yet with modules, this is not the case:
>
> module M
>  def self.goodbye
>    puts "goodbye"
>  end
> end
>
> class A
>  include M
> end
>
> A.goodbye #=> NameError


class A
  include M
  include N
end

now, which goodbye??

> To get around this limitation many ppl resort to this ugly hack:

sorry, ' prefer specs over hacks :-)

module ClassMethods
  def goodbye
    puts "goodbye"
  end
end
#=> nil

class A
  class << self
    include ClassMethods
  end
end
#=> #<Class:A>

A.goodbye
goodbye

clearer, if i may say.

best regards -botp