From: ptkwt@... (Phil Tomson)
Date: 2006-02-15T16:48:26+09:00
Subject: Re: extend quesion

In article <200602150449.40928.david@vallner.net>,
David Vallner  <david@vallner.net> wrote:
>D=C5=88a Streda 15 Febru=C3=A1r 2006 03:23 Phil Tomson nap=C3=ADsal:
>> I think the answer is that A has already been mixed-in so it's not really
>> mixed-in again (true?).=20
>>
>
>Quite so.
>
>> And how would I go about making this work so that it prints:
>>
>> A::foo
>> B::foo
>> A::foo
>>
>> ?
>>
>
>Make the message printed an instance attribute and change it? *duck*
>
>Mixins aren't plain supposed to do that. They are to add methods, not rewri=
>te=20
>them at whim. 

Yeah, I just thought it would be a nice, fairly easy solution.  

>If you -have- to do this via metaprogramming, use singleton=20
>methods. 

Yeah, I could probably do something like that by redefining the method...

(BTW: Using extend as above makes foo a singleton method )

> Especially in non-trivial code, heavy use of #extend to change=20
>behaviour over and over again would get really messy.

The only way to really get it to work would be to remove_method before doing 
the extend.  The problem with that is that remove_method doesn't work in that 
context (removing singleton methods).

I should probably consider some sort of delegation pattern instead.  One 
fairly easy way would be to use method_missing and then change the target 
object of the message (though I want to avoid overuse of method_missing because 
1) it can make things difficult to debug and 2) I might need it for another 
purpose in this application. )

Phil