"Gary Chambers" <gazzaguru2 at btinternet.com> wrote in message

>> A>>setFoo: aFoo
>>     Undoable newOn: [ foo := aFoo ]

> Have a look at the Command and CommandHistory clasees. Worked well for our
> Report Builder...

I am hoping to find a way for Undoable to dynamically extend a few 
primitives (e.g. assiging to an instVar or indexedVar, probably adding or 
removing indexedVars, others??).

========== e.g. currently:

Object>> instVarAt: anInteger put: anObject
 <primitive: 74>
 ^self basicAt: anInteger - self class instSize put: anObject

========== Dynamically change to:

Object>> instVarAt: anInteger put: anObject
  self recordIVarChange: anInteger oldVal: self instVarAt: anInteger.
  self primInstVarAt: anInteger put: anObject

Object>> primInstVarAt: anInteger put: anObject
 <primitive: 74>
 ^self basicAt: anInteger - self class instSize put: anObject

===========
Then #recordIVarChange can put undoable/redoable records on the stack.

Does this sound feasible? Scary to dynamically re-define primitive methods, 
don't know where to start :-(

Sophie