You'd need to be very careful... and probably need to redefine
instVarAt:put: in the object that handles the command/undo to do the normal
thing (to avoid recursion).

Of course, assignments to ivars in methods won't actually call
instVarAt:put: (done in the bytecode I believe).

Can you explain the general functionality you are hoping to obtain?

Gary.


> -----Original Message-----
> From: squeak-dev-bounces at lists.squeakfoundation.org
> [mailto:squeak-dev-bounces at lists.squeakfoundation.org]On Behalf Of
> itsme213
> Sent: 30 April 2008 3:22 PM
> To: squeak-dev at lists.squeakfoundation.org
> Subject: [squeak-dev] Re: Undoable environment ?
>
>
> "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
>
>
>
>
>