From: Paul Hanchett <paulha@...>
Date: 2005-04-10T05:59:40+09:00
Subject: Re: method search rule in 2.0?

David A. Black wrote:
> Hi --
> 
> On Sat, 9 Apr 2005, David Garamond wrote:
> 
>> I read:
>>
>>
>> http://pub.cozmixng.org/~the-rwiki/rw-cgi.rb?cmd=view;name=Ruby2.0MethodSearchRuleEnglish 
>>
>>
>> and was feeling disturbed about this new Ruby2 behaviour.
>>
>> class C
>>   def process
>>     # ...
>>     util
>>   end
>>
>>   def util
>>     # ...
>>   end
>> end
>>
>> class CC < C
>>   def util
>>     # ...
>>   end
>> end
>>
>> CC.new.process # C#process expects C#util,
>>                # but calls CC#util
>>
>> Why is this a problem? Isn't it what people expect in OO? I'm not an 
>> OO expert, but isn't this one of the supposedly unique feature/benefit 
>> of OO: allowing old code to call new code. I believe it's called 
>> polymorphism?
>>
>> Now Ruby2 wants to change so that 'util' in C method calls C#util and 
>> 'self.util' calls CC#util. I very much prefer 'self.util' to be the 
>> one that calls C#util (and I don't think I'll ever use it a lot). The 
>> latter is backwards compatible and how virtually all other languages 
>> behave.
> 
> 
> I agree that the non-special case should be what it is now, and the
> case where you don't want overriding should be the one that requires
> something extra.  But I don't think it should be based on overloading
> "self" (and I believe having "self" refer to the class context, rather
> than the object, is a kind of overloading).  If this mechanism is
> really necessary, I would rather see:
> 
>   class C
>     def process
>       # ...
>       C#util
>     end
>   end
> 
> which is, I think, a more direct way of saying: protect this call from
> overriding in subclasses.  (Yes, everybody, I do know that this is
> comment syntax and would require a parser change :-)

If I was writing class C, I would be surprised when CC#util got called, 
but that is exactly the OO behavior you want sometimes.  I think both 
the naked call to util and self.util should be relative to the 
/instantiated/ object.

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

Paul