Hi,

Remember there is MetaclassTalk  
(http://csl.ensm-douai.fr/MetaclassTalk) that provides explicit  
metaclasses and other reflective facilities for Squeak. You can define  
your own metaclasses and use them in order to have classes with the  
following protocole :

Object subclass: #Person
	instanceVariableNames: 'name age '
	classVariableNames: ''
	poolDictionaries: ''
	category: 'MetaclassTalk-Examples'
	metaclass: MyMetaclass	

One intersting application of explicit metaclasses I did is to  extend  
Smalltalk with mixin-based inheritance.
However, neither implicit metaclasses (with parallel hierarchies) nor  
explicit metaclasses are totally satisfactory. Actually, there should  
be a mix of both (see my papers on metaclass compatibility OOPSLA98,  
ESUG2003).

Noury
Le 16 févr. 06, à 19:37, Bergel, Alexandre a écrit :

> Today I spend some time to read and understand an old mail from  
> Andreas  
> (http://lists.squeakfoundation.org/pipermail/squeak-dev/2005-October/ 
> 096370.html) about having a parallel metaclass hierarchy. I really  
> like this.
>
> Thanks Andreas!!
>
> I wrote a short test to understand it, I think it might interest some  
> of you:
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> testClassCreation
> 	"self debug: #testClassCreation"
> 	| mcls cls |
>
> 	mcls := MyMetaclass
> 		subclass: #MC
> 		instanceVariableNames: ''
> 		classVariableNames: ''
> 		poolDictionaries: ''
> 		category: 'MyMetaClassesGenerated'.
> 	cls := MyObject
> 		subclass: #C
> 		instanceVariableNames: ''
> 		classVariableNames: ''
> 		poolDictionaries: ''
> 		category: 'MyMetaClassesGenerated'
> 		metaclass: mcls.
> 	classCreated addAll: {mcls . cls}. "Used in teardown to remove the  
> classes"
> 	
> 	mcls compile: 'foo ^20'.
> 	
> 	self assert: (cls new class == cls).
> 	self assert: (cls class name = 'C class').
> 	self assert: (cls class class == mcls).
> 	self assert: (cls class class class class == MyMetaclass).
> 	self assert: (cls class soleInstance == cls).
>
> 	self assert: (cls canUnderstand: #foo) not.
> 	self assert: (cls class respondsTo: #foo).
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>
> Cheers,
> Alexandre
> -- 
> _,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:
> Alexandre Bergel  http://www.cs.tcd.ie/Alexandre.Bergel
> ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;.
>
>
>
>
--------------------------------------------------------------
Dr. Noury Bouraqadi - Enseignant/Chercheur
Ecole des Mines de Douai - Dept. G.I.P
http://csl.ensm-douai.fr/noury

European Smalltalk Users Group Board
http://www.esug.org

Squeak: an Open Source Smalltalk
http://www.squeak.org
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