On Aug 21, 2012, at 3:53 AM, Andreas Grosam wrote:
> So, in order to implement KVO, I would need to track changes of the ivar
> _state, and invoke
> -willChangeValueForKey:, and
> -didChangeValueForKey:
> appropriately.
>
> But, how exactly can I accomplish this with the given code above?
You can call will/did around a change which doesn't actually change the value,
so it becomes straightforward.
Also, especially if the number of fields grows, you may want to have a KVC
"state" property (not necessarily public), and use
+ (NSSet *)keyPathsForValuesAffectingFoo / Bar; { return [NSSet
setWithObject:@"state"]; }
That way you only need to do will/didChangeValueForKey:@"state" and the other
KVO methods get triggered as well, instead of having to next multiple will/dids
for each key (foo, bar, blah, blah) around every state change.
--
Seth Willits
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