In SkinScript such as
WHEN eventspec CALL expression SAVING mementolist
if any of the mementos in mementolist are not found, the script raises a
KeyError.
I'd like a way of saving a memento if it exists, or NOT_FOUND otherwise.
For example, an Executive might have a CompanyCar.
WITH CompanyCars.getCar(self.car_id) or NOT_FOUND COMPUTE
car=RESULT,
car_registration=registration
OTHERWISE LET
car=NOT_FOUND,
car_registration="no car"
When an Executive changes her car for a different one, I want to perform
certain actions on the old car, and certain on the new car:
WHEN OBJECT CHANGED CALL
HAS_CHANGED('car_id') and
(self.car_id and CompanyCars.getItem(self.car_id).decommission(),
ORIGINAL['car_id'] and OLD['car'].commission())
SAVING car
However, I can't do this if the executive is being assigned a car from a
state of having no car. It fails with a KeyError because the ZPatterns
machinery can't save "car".
--
Steve Alexander
Software Engineer
Cat-Box limited
http://www.cat-box.net
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