From: Pit Capitain <pit@...>
Date: 2005-05-09T16:11:04+09:00
Subject: Re: Method hooks in singleton classes

Hi Matz, Nobu and Florian,

thank you all for your replies.


Nobu wrote:
> What will you need if method_added is redefined too?

As Florian answered already, this would invoke singleton_method_added, 
as it does today. You had to redefine both singleton_method_added and 
the singleton class' method added at the same time.


Matz wrote:
> In that case, we have to decide to make "metaclass" in the language
> specification.  See [ruby-talk:139309].

Ah, I see. You can implement singleton methods without having singleton 
classes in the language, as you often had mentioned. But currently it 
*is* possible to access singleton classes, and they *are* class objects. 
They are special classes in the sense that you can't instanciate them, 
but I don't see why they should be even more special by removing 
method_added et al. And I don't feel that adding this behavior would 
make singleton classes more present in the language than they are today. 
But of course this is only *my* feeling.

> I'm not sure it's the solution.  We sometimes want to avoid
> redefinition.  Something like "around" method in CLOS might help.

This is exactly what I'm trying to implement. I want to reliably add 
before, after or around methods and keep them when redefining a method. 
I know that something like this will come with Ruby 2, but I'd like to 
have it sooner.

Regards,
Pit