From: Paul Hanchett <paulha@...>
Date: 2005-04-10T07:19:44+09:00
Subject: Re: method search rule in 2.0?

David A. Black wrote:

>> If I really want to call C#util, why not say C::util?  It seems like 
>> anything else has compatibility problems...
> 
> 
> C::util is a class method call,

But if C#util is not defined as a with "def C.util ..." isn't it just a 
regular method?  Or is C::util really a different sort of call to the 
class object?

> but what we're talking about here
> pertains to instance methods.  The idea of C#util is not to call
> C::util, but to call util on the instatiated object -- constraining
> that call so that it is the #util defined in class C, not class CC.
> 
>   class C
>     def x
>       puts "I'm the #x from C"
>     end
> 
>     def y
>       x    # call the most recently defined #x at the time of the call
>     end
> 
>     def z
>       C#x  # call the x defined in C, no matter what
>     end
>   end
> 
>   class CC < C
>     def x
>       puts "I'm the #x from CC"
>     end
>   end
> 
>   CC.new.y    # I'm the #x from CC
>   CC.new.z    # I'm the #x from C
> 
> Note that having a CC object "call the x defined in C" is different
> from saying "Call the class method C.x" (which doesn't exist at all).

Allowing an inheriting class to call an ancestor method without 
inheriting it (i.e., skipping the inheritance chain) is not a good idea, 
I think.  Of course with Ruby you can retroactively redefine existing 
methods on instantiated objects, right?  (I'm a Ruby NOOB, so I may have 
that wrong!)

An underlying assumption about OOD is that ancestor classes don't need 
to worry about descendent classes changing the meaning of methods 
defined by the ancestors.

I think we will have to pick our poison-- Either there has to be a 
declaration /in the class defintion/ whether a particular method is 
virtual of not (C++), or we choose an object model where all methods are 
virtual (Java and Python) or not (VB, I think).

Paul