From: Rick DeNatale <rick.denatale@...>
Date: 2009-05-26T00:49:01+09:00
Subject: Re: Class methods in a module?

On Mon, May 25, 2009 at 11:07 AM, Max Williams
<toastkid.williams@gmail.com> wrote:
> At Scotland On Rails a few months ago, I was shown a nice way to put
> class methods in a module, alongside instance methods, in such a way as
> they will get added as class methods automatically, without any work
> required on the part of the person including the module.
>
> Unfortunately i failed to make a note of how to do this and i've since
> forgotten.  Can anyone show me?
>
> It was something along these lines...(the following doesn't work btw)
>
> module Mappable
>
>   #instance methods
>   def foo
>     "foo"
>   end
>
>   #class methods
>   class << self.class
>     def bar
>       "bar"
>     end
>   end
>
> end
>
> can anyone set me straight?
> thanks
> max


The usual way is to use the hook method Module#included, something like:

module Mappable

  #instance methods
  def foo
    "foo"
  end

  #class methods
  module ClassMethods
    def bar
      "bar"
    end
  end

  def self.included(other)
     other.extend(ClassMethods)
  end
end

By the way this nesting of a Module inside a module is another variant
on something discussed in another recent ruby-talk thread.
-- 
Rick DeNatale

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