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[Help-smalltalk] Re: [patch] Enhance to kernel/

From: Paolo Bonzini
Subject: [Help-smalltalk] Re: [patch] Enhance to kernel/
Date: Tue, 27 Oct 2009 09:16:07 +0100
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On 10/27/2009 04:40 AM, Lee Duhem wrote:
Subclasses of nil? I didn't understand what this means,  can you explain further
or point to some documents?

While 99% of the classes are subclasses of Object, it is also possible to create classes that do not inherit from anything (or equivalently, whose subclass is nil). In this case, the metaclass will be a subclass of Class; so I used in my example "Class allSubclassesDo:" to get the metaclasses (which provide class-side methods), and go to the classes (which provide the instance side) by sending #asClass.

There is a small part in the tutorial on this topic; alternatively, you may see if you find a presentation called "The Behavior of Behavior".

By the way, the reason why I didn't like #allSuperclasses is the following. The #superclass and #subclasses methods return the classes that are "adjacent" (one level up or one level down) in the hierarchy. Prefixing "all" gives also the indirect superclasses/subclasses. #superclasses then would be a method that returns an array of direct superclasses (which would have a single element, since Smalltalk only has single inheritance).


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