Re: [NSObject setValue:forUndefinedKey:] no longer requires explicit KVC notifications?
Re: [NSObject setValue:forUndefinedKey:] no longer requires explicit KVC notifications?
- Subject: Re: [NSObject setValue:forUndefinedKey:] no longer requires explicit KVC notifications?
- From: Ken Thomases <email@hidden>
- Date: Sun, 9 Aug 2009 07:35:37 -0500
On Aug 8, 2009, at 6:24 PM, Gabriele de Simone wrote:
On Aug 8, 2009, at 2:37 PM, Keary Suska wrote:
It used to be that if you overrode -[NSObject
setValue:forUndefinedKey:] your own subclass was responsible for
calling -[NSObject will/didChangeValueForKey: so that bindings and
observers would work as expected.
That was fine, since it allowed one to provide different
implementations depending on the key, and to generate (or not) KVC
notifications. It seems that a recent update to Mac OS X (perhaps
10.5.8?) has changed this behavior. It seems that as long as you
override setValue:forUndefinedKey:, KVC-compliant notifications are
automatically generated for the given key.
Can anyone confirm this? This is an "interesting" change to the
Cocoa framework that probably interferes with any class that
overrides [NSObject setValue:forUndefinedKey:].
Calling will/didChange should never have been necessary, and in fact,
the setter sequence should be automatically wrapped with the calls,
as
long as automatic notification is on. AFAIK, this has always been the
case and hasn't changed recently. There may be more side effects than
before, but I don't recall.
HTH,
Keary Suska
Esoteritech, Inc.
"Demystifying technology for your home or business"
The KVC infrastructure did not always generate value-changed
notifications for setValue:forUndefinedKey: overrides.
The setValue:forUndefinedKey: override should have nothing to do with
it. It's the setValue:forKey: call -- the one which provokes the call
to setValue:forUndefinedKey: -- that's responsible for triggering the
KVO change notifications.
Doubting my own sanity (always a good approach, IMO) I searched for,
and found some evidence of this in an old discussion:
http://www.cocoabuilder.com/archive/message/cocoa/2006/10/12/172593
That thread doesn't confirm what you're saying. It says the
opposite. It says what I just said. If you override setValue:foKey:
_then_ you lose automatic KVO notifications and would have to
reimplement them yourself, but if you just override
setValue:forUndefinedKey: you don't have that problem.
Regards,
Ken
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