From: "David A. Black" <dblack@...>
Date: 2007-09-26T23:31:46+09:00
Subject: Re: difference between inheritance and mixin

Hi --

On Wed, 26 Sep 2007, Phrogz wrote:

> On Sep 26, 12:06 am, Vellingiri Arul <hariharan....@rediffmail.com>
> wrote:
>> Hai friends,
>>       Can anybody can answer this question.
>> what is the difference between inheritance and mixin.
>>     what is the use of mixin and what is the use of inheritance.
>
> Mixin modules are searched before the parent class.
> http://phrogz.net/RubyLibs/RubyMethodLookupFlow.png
>
> Also, you can only inherit from one parent class, but you can mixin
> many modules to the same class.
>
> Because modules cannot inherit from other modules or classes, there is
> no problem of 'diamond' inheritance.

Modules can mix in modules, though, so you could have:

              module M

     module N         module O

               class C


But the diamond problem is avoided by having the order of mixing in be
significant, so that there's no ambiguity about which module/class is
to be searched.


David

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