Hmm. VisualWorks has namespaces, which Smalltalk-80 does not, and they seem to have changed the way subclasses are defined. According to my copy of the purple book, a subclass is created by sending a class the message ‘subclass:’. It should be possible to implement a version of subclass in the Creature class that adds the extra code.

However, VisualWorks wants me to send ‘defineClass:’ to a namespace. Problem with that is I want to change the way subclasses of a particular class are defined. If I change the code in the NameSpace class that will affect every class that is ever created thereafter.

I hope VisualWorks hasn’t sacrificed this flexibility. I think that the original implementation was the correct one (classes create their children), and that it should have been possible to introduce namespaces without changing it, or at least get the method in NameSpace to delegate to the original code. Currently both mechanisms exist, although the original one appears to have been left there just for backwards compatibility.

Hopefully James or someone who knows more about VisualWorks than I do will read this and set me straight.

Added later: James happily responded. How many other product managers would personally respond to some random blogger’s idle meanderings?