From: Trans <transfire@...>
Date: 2007-02-19T11:49:24+09:00
Subject: Re: More flexible inheritance



On Feb 17, 8:40 pm, "Andrew Stone" <stoneli...@gmail.com> wrote:
> Trans,
>
> I'm actually in the middle of a week long argument concerning "fat models"
> versus "thin models" and with my approach being fat libraries and thin
> models.

That's a long argument ;)

> We have a few sites which will share a lot of functionality and
> instead of sharing the models, I like sharing libraries that are included in
> the models.  The idea being that this is easy to do with svn externals on
> the lib directory.  Then fix a bug or add functionality in one place.  Even
> though this gives two places to look for methods, I think it's nice and
> clean.
>
> Even though my example is for a specific implementation, the idea of classes
> becoming containers of modules is a great solution to sharing functionality.

I think yours is a perfect example. Modules provide SOC and
consequently allow one to more easily mix and match aspects to
different models. That a class would become exclusively a container of
modules (anonymous or explicit) at the very least helps promote a good
practice.

The only substantial argument against such an approach I've come up is
one in preference of delegation over inheritance. If available aspects
are modules rather than classes then we are sort-of pushed toward
using inheritance, even though in some cases delegation would be
preferable. However it's easy enough to maneuver around this if need
be, for example:

  class Module
    def new(*a,&b)
      base = self
      Class.new{ include base }.new(*a,&b)
    end
  end

> I'm pleased to hear others are thinking this way.

Me too.

T.