From: Joel VanderWerf <vjoel@...>
Date: 2001-10-09T14:20:09+09:00
Subject: [ruby-talk:22280] Re: Ruby and multiple inheritance

ts wrote:
> 
> >>>>> "J" == Joel VanderWerf <vjoel@PATH.Berkeley.EDU> writes:
> 
> J> Base#foo called in this way cannot affect the instance vars of Derived.
> 
>  I can't understand why a module must affect an instance variable which
>  will be defined in a class which include this module. Bad design for me.

Ok, maybe that's a bad example. But it applies to instance methods as
much as to instance variables. That's a real problem, since the concept
of mixin (like Enumerable) depends on the module being able to call
instance methods (like each) that will be defined in a class which mixes
in the module.

My point is that "M.foo" (where M is an included module) ishould not be
looked at as a generalization of "super" that lets you specify which
included module to use, in the style of C++. As someone wisely pointed
out, mixin is a different beast from MI, neither bigger nor smaller, but
equally hairy.

This is a good reason to avoid name conflicts between mixins.

--
Joel VanderWerf                          California PATH, UC Berkeley
mailto:vjoel@path.berkeley.edu                     Ph. (510) 231-9446
http://www.path.berkeley.edu                       FAX (510) 231-9512