But shouldn’t the synthesized accessors automatically return such a proxy object? No. What’s the proper way to work around this–should I write a custom accessor that just invokes [super mutableArrayValueForKey…]? No. Implement the array accessors. When you call these, KVO will post the appropriate notifications automatically. So all you have to do is: [myObject insertObject:newObject … Read more
There are usually notifications or other observable events where KVO isn’t supported. Even though the docs says ‘no’, it is ostensibly safe to observe the CALayer backing the UIView. Observing the CALayer works in practice because of its extensive use of KVO and proper accessors (instead of ivar manipulation). It’s not guaranteed to work going … Read more
You still can implement -dealloc under ARC, which appears to be the appropriate place to remove the observation of key values. You just don’t call [super dealloc] from within this method any more. If you were overriding -release before, you were doing things the wrong way.
Put a try catch around your removeObserver call @try{ [someObject removeObserver:someObserver forKeyPath:somePath]; }@catch(id anException){ //do nothing, obviously it wasn’t attached because an exception was thrown }
Encapsulation If the ivar is private, the other parts of the program can’t get at it as easily. With a declared property, the clever people can access and mutate quite easily via the accessors. Performance Yes, this can make a difference in some cases. Some programs have constraints where they can not use any objc … Read more
These are good questions, and its great to see that you’re doing this research and seem concerned with learning how to “do it right” instead of just hacking it together. First, I agree with the previous answers which focus on the importance of putting data in model objects when appropriate (per the MVC design pattern). … Read more
You can use KVO in Swift, but only for dynamic properties of NSObject subclass. Consider that you wanted to observe the bar property of a Foo class. In Swift 4, specify bar as dynamic property in your NSObject subclass: class Foo: NSObject { @objc dynamic var bar = 0 } You can then register to … Read more