From: Paul Brannan <pbrannan@...>
Date: 2002-10-19T02:01:19+09:00
Subject: Re: Interfaces in Ruby

On Fri, Oct 18, 2002 at 11:21:17PM +0900, Chris Gehlker wrote:
> I consider mixins to be a *form* of MI. I would go so far as to say 
> that it is the only form that I've actually seen usefully employed even 
> in C++ code. Your example below and your previous example with is_a 
> show that it passes the duck test. But even if you want to consider the 
> it to be "the illusion of multiple inheritance" it's important to 
> maintain the illusion. Which is why I think it important to use class 
> clusters as well as mix-ins.

I think it's possible to maintain this illusion, provided:
  1) No two modules mixed into the same class provide two methods with
     the same name
  2) Mixins do not carry any state (and therefore have no initialize()
     method); this is a special case of the first requirement.

I have not yet decided whether I think it is always a good idea to
strictly adhere to these requirements.

Paul