On May 11, 2010, at 12:45, Joanna Carter wrote:
> Only if you implement the KVO pattern in the setters:
>
> - (void) setCornerSize:(NSSize) _size
> {
> [self willChangeValueForKey:@"CornerSize"];
> [[self cell] setCornerSize:_size];
> [self didChangeValueForKey:@"CornerSize"];
> }
Um, not so much. :)
In the normal case, setters *should not* call will/didChangeValueForKey, since
the entire setter is (invisibly) enclosed in a pair of such calls. It's
harmless (AFAIK), because KVO explicitly suppresses the recursion implied by
calling them within the setter, but it's absolutely unnecessary. Unless ...
If the property is explicitly marked to not generate KVO notifications
automatically, you will of course need to call will/didChangeValueForKey
manually. See here:
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/KeyValueObserving/Concepts/AutoVsManual.html
The *only* case of this you'll run into normally is Core Data: all of its
properties are not subject to automatic KVO notification triggering. (Whether
it's via 'automaticallyNotifiesObserversForKey:' or via some private mechanism
is not documented.)
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