[Gbbopen-list] deleted-unit-instance

[Paul Werkowski]

The recent side effect of delete-instance changing the class of
the instance to deleted-unit-instance and thereby losing all
state information was not anticipated here. I have worked around
this change by guarding calls to slot references with
deleted-unit-instance-p but am not sure at this point how broken
my application really is.

Having object state available (when the deleted state was just
an attribute) was very handy during debugging and letting application
code access non blackboard object state of a deleted instance
seemed useful.

Is it possible for a delete-instance-event handler to
intercede and change the class of the instance to preserve non-BB state?

Example; if exists non BB class location and a BB class
(define-unit-class location-unit (location standard-unit-instance)())

then (delete-instance (make-instance 'location-unit))
results in an object of class location?

Paul

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