On Nov 17, 2008, at 22:54, John Clayton wrote:
I'm basically looking to restore some state on an object at time of
deletion, e.g.
if A is associated with B via a to-many relationship from A->B, then
when one instance of B is deleted - we need to change a property on A.
If a B is delete, what causes it to be removed from the A->B
relationship? If B's delete rule is set to "nullify" then it's
automatically removed from the relationship. Otherwise, you must be
doing something explicit to remove the deleted B from the
relationship, yes?
Either way, it sounds like you what *really* want is to know when a B
is removed from the relationship. If so, you could have A observe its
relationship property, and recalculate the dependent property when you
get a KVO notification.
That would mean you'd also do the recalculation when you remove a non-
deleted B from the relationship (if that ever happens, but if it does
you may not care).
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