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

[Paolo Bonzini]

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).

Paolo