On 2 Sep 2009, at 13:47, Kevin Brock wrote:
Likewise, there's never been any guarantee that invoking -
observeValueForKeyPath:ofObject:change:context: will provoke the
receiver to call -valueForKeyPath: on the object whose property has
changed. If the observer wants, it can rely totally on the
information in the change dictionary. If you were using will/
didChange..., then KVO can be expected to invoke valueForKey: on
the object whose property is changing, but that's not what (you
say) you're doing.
Thanks. That was helpful. On 10.5 the receiver *does* apparently
always call valueForKeyPath, at least with the receivers we're
talking to. Maybe they weren't checking the dictionary on 10.5, or
were calling the fn if the data on the new values wasn't found in
the dictionary, but are being stricter on 10.6.
Ken didn't contradict the behaviour you have observed. But you are
[were] relying on a mechanism that is undocumented and quite possibly
accidental on the part of Apple's engineers, and so could have changed
at any time, or might have been erratic/fragile even on 10.5.
In other words, it is merely fortunate that your app ever worked on
10.5, and not by design ;-)
The documented pattern that Ken described should work on both 10.5 and
10.6, and will always work... until deprecated anyway!
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