From: Robert Klemme <bob.news@...>
Date: 2005-12-31T20:03:24+09:00
Subject: Re: get mixin's name

Payton Swick <payton@foolord.com> wrote:
> The goal was basically this for a GUI (the answer is probably that
> there's a better way):
>
> module Layout
> # ... layout stuff
> def layout_name
> 'none'
> end
> end
>
> module CoolLayout
> include Layout
> # ... override some layout stuff.
> def layout_name
> 'CoolLayout' # Not DRY
> end
> end
>
> class Window
> def layout=(l)
> extend l
> end
> end

IMHO this is a bad idea because you cannot change layout that way multiple 
times.  Once you extended an instance by a module this module stays in place 
even if you extend with a different module.  Also, a Window *has* a layout - 
so composition is far more appropriate here than inheritance.  And if you do 
that and model layouts as independent class hierarchy you can simply use the 
layout instance's class or it's name for the layout name.

> a = Window.new
> a.layout = CoolLayout
> puts "This window has the layout #{a.layout_name}"

I'd prefer to let the layout answer the question after its name which also 
nicely fits with the composition approach - and it helps keep the interface 
of Window focused:

puts "This window has the layout #{a.layout.name}"

Kind regards

    robert