Key Value Observing and NSButton state

Question

I'm trying to observe checkbox status and make appropriate changes in the app when checkbox status changes. In a window manager that manages the window with checkbox I have following observer setup:

- (void)awakeFromNib
{
  [myCheckBox addObserver:self 
                  forKeyPath:@"state" 
                     options:(NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld) 
                     context:NULL];
}

- (void)dealloc
{
  [myCheckBox removeObserver:self forKeyPath:@"state"];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
  NSLog(@"KeyPath: %@", keyPath);
  NSLog(@"ofObject: %@", object);
  NSLog(@"change: %@", change);
}

I also have wired up myCheckBox to file owner (which is window controller) to appropriate checkbox in the window. However when I run my app observeValueForKeyPath:ofObject:change:context: method is never called.

What am I doing wrong?

Answer 1

In -awakeFromNib check that myCheckbox is not nil. If it's nil then it's not connected properly in IB.

Edit: NSButton.state has the same value as NSButton.cell!.state, but it isn't Key-Value Observable. To be able to observe the value, you'll need to use the \.cell!.state key path.