From: Daniel Berger <Daniel.Berger@...>
Date: 2006-04-11T07:25:07+09:00
Subject: Re: Adding both class and instance/object methods from a Module?

ara.t.howard@noaa.gov wrote:
> On Tue, 11 Apr 2006, Sam Roberts wrote:
> 
>> On Tue, Apr 11, 2006 at 02:46:24AM +0900, zdennis wrote:
>>>> Is there an easy way to extend classes with both class and object
>>>> methods at the same time?
>>
>>>   irb(main):010:1*   def self.included( clazz )
>>>   irb(main):011:2>      clazz.extend( ClassLevelAddons )
>>>   irb(main):012:2>   end
>>>   irb(main):013:1> end
>>>
>>> The above lets M take care of the work, so your class doesn't have to
>>> think about it. This is the method that Robert Klemme was refering to,
>>> Module::included
>>
>> I was hoping that I was missing some clever way to do it with just one
>> module. Guess not. But the self.included hook is a good idea.  The two
>> modules become an implementation detail, and thats good enough.
> 
> you can do it with one:
> 
> 
>   harp:~ > cat a.rb
>   module M
>     def a
>       self
>     end
>     def self.included other
>       other.extend self
>       super
>     end
>   end
> 
>   class C
>     include M
>   end
> 
>   p C.a
>   p C.new.a
> 
> 
>   harp:~ > ruby a.rb
>   C
>   #<C:0xb75d0a20>
> 
> 
> regards.
> 
> -a

I'm coming into this thread late, but I think I'm missing something here. 
What's wrong with this?

module Foo
    attr_accessor :meth_a
end

class Bar
    include Foo
    extend Foo
end

p Bar.meth_a # nil
Bar.meth_a = 'test'
p Bar.meth_a # 'test'

bar = Bar.new
p bar.meth_a # nil
bar.meth_a = 'test'
p bar.meth_a # 'test'

Regards,

Dan