From: Shilesh Kumar <shyl.sk@...>
Date: 2008-09-17T16:57:28+09:00
Subject: Re: SuperClass and Modules

James Coglan wrote:
>>
>> Multiple inheritance has one big problem usually denominated as "the
>> diamond problem". Check this link:
>> http://en.wikipedia.org/wiki/Diamond_problem.
>> Ruby using single inheritance plus mixins gives almost the same
>> advantages without these problems.
> 
> 
> 
> You cannot have multiple inheritance without the diamond problem -- that
> page actually mentions how Ruby resolves method names in this case:
> 
> module A; end
> module B; include A; end
> module C; include A; end
> 
> class D
>   include B
>   include C
> end
> 
> Methods will be looked up in D, C, B and A (in that order) when you call 
> a
> method on an instance of D.

Thanks James and Pedro,

I understood the diamond problem.

let me clarify myself.

To avoid the method confusion while having more than one module, Ruby 
looks in a particular order. This can be applied in the case of super 
classes as well and let ruby follow the order of import while searching 
for a method. Thus i may have,

class MyClass < A < B #[oder of method search will be from MyClass, A to 
B]

I believe that there might be some strong reason for allowing multiple 
Modules while restricting only one Parent ...?
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