Ah. You’re observing a TekkPoint object from a SomethingElse object, and the SomethingElse object is the one adding and removing the observers, correct? (That’s the normal way things are done; I’m just trying to clarify.) It looks like your TekkPoint object is being deallocated while the SomethingElse that’s observing it is still around. The SomethingElse … Read more
You have an object that got dealloc’ed and did not stop observing another object. Walk through all of your -addObserver… calls and make sure they are matched with -removeObserver… calls at least in the -dealloc and possibly in the -viewDidUnload depending on your application structure.
KVO works with setter and getter and in incNumber you are directly accessing iVar so instead of that use self.number – (IBAction)incNumber:(id)sender { self.number++; NSLog(@”%d”, self.number); }
In iOS 11, you don’t have to. Just let the observer go out of scope. There is no penalty any longer for letting an observer die before the observed or for letting the observed die before the observer, so you have no actual work to do. On the other hand, if you really want to … Read more
[…] is it possible to check if an object actually is observing that property? No. When dealing with KVO you should always have the following model in mind: When establishing an observation you are responsible for removing that exact observation. An observation is identified by its context—therefore, the context has to be unique. When receiving … Read more
Use a delegate if you want to talk to only one object. For example, a tableView has a delegate – only one object should be responsible for dealing with it. Use notifications if you want to tell everyone that something has happened. For example in low memory situations a notification is sent telling your app … Read more
The important thing is (generally speaking) that you use something (as opposed to nothing) and that whatever you use be unique and private to your use of it. The primary pitfall here happens when you have an observation in one of your classes, and then someone subclasses your class, and they add another observation of … Read more
Swift 4 introduced a family of concrete Key-Path types, a new Key-Path Expression to produce them and a new closure-based observe function available to classes that inherit NSObject. Using this new set of features, your particular example can now be expressed much more succinctly: self.observation = object.observe(\.keyPath) { [unowned self] object, change in self.someFunction() } … Read more
You need to add to your UIDatePicker the UIControlEventValueChanged event to handle date changes: [myDatePicker addTarget:self action:@selector(dateIsChanged:) forControlEvents:UIControlEventValueChanged]; Then the implementation: – (void)dateIsChanged:(id)sender{ NSLog(@”Date changed”); }