Changing the Class of an Object

Stephen Pair spair at
Thu Dec 14 04:06:37 UTC 2000

Here's a change set that will do the'll need to compile a new
VM.  It adds a method Object>>class:

This was based on some other work involving explicit metaclass
programming...can't remember who it was though.

- Stephen

> -----Original Message-----
> From: Andrew P. Black [mailto:black at]
> Sent: Wednesday, December 13, 2000 8:08 PM
> To: Squeak Mailing List
> Subject: Changing the Class of an Object
> I've been looking at porting to Squeak some cunning code written by
> Stephane Ducasse.  The idea is to intercept messages sent to a
> particular object by creating for that object a rudimentary class
> (actually a subclass of Behavior) that inherits from the objects real
> class but has new definitions for the intercepted messages.  These
> definitions can do super-sends to get the normal behavior.
> The question that I have is: is there a way in Squeak to change the
> class of an object, the equivalent of IBM Smalltalk's  fixClassTo:
> The only way that I know of doing this would be to make a new object
> that is an instance of the desired class, copy the slots, and use
> become:.  But this is obviously very expensive!  What I would like to
> do is just "overwrite the class pointer".  But I can't see a way of
> getting at it.
> Any suggestions?
> 	Andrew
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