How can i tell if an object has a key value observer attached

Question

if you tell an objective c object to removeObservers: for a key path and that key path has not been registered, it cracks the sads. like -

\'Cannot remove an observe

Answer 1

In my opinion - this works similar to retainCount mechanism. You can't be sure that at the current moment you have your observer. Even if you check: self.observationInfo - you can't know for sure that you will have/won't have observers in future.

Like retainCount. Maybe the observationInfo method is not exactly that kind of useless, but I only use it in debug purposes.

So as a result - you just have to do it like in memory management. If you added an observer - just remove it when you don't need it. Like using viewWillAppear/viewWillDisappear etc. methods. E.g:

-(void) viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [self addObserver:nil forKeyPath:@"" options:NSKeyValueObservingOptionNew context:nil];
}

-(void) viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [self removeObserver:nil forKeyPath:@""];
}

And it you need some specific checks - implement your own class that handles an array of observers and use it for your checks.