Cocoa - Notification on NSUserDefaults value change?

Question

Let's say I have a key @"MyPreference", with a corresponding value stored through NSUserDefaults.

Is there a way to be Notified when the value is modified?

Or could it be done through bindings? (But this case, instead of binding the value to a UI element, I wish my object to be notified of the change, so that I can perform other tasks.)

I am aware that NSUserDefaultsDidChangeNotification can be Observed, but this appears to be a all-or-nothing approach, and there does not appear to be a mechanism there to get at the specific key-value-pair that was modified. (Feel free to correct.)

Answer 1

Spent all day looking for the answer, only to find it 10 minutes after asking the question...

Came across a solution through Key-Value-Observing:

[[NSUserDefaultsController sharedUserDefaultsController] addObserver:self
    forKeyPath:[@"values." stringByAppendingString: @"MyPreference"]
    options:NSKeyValueObservingOptionNew
    context:NULL];

Answer 2

Why are you appending a string literal to a string literal instead of just writing the whole thing as one?

Answer 3

And Apple employee advised to use NSUserDefaultsDidChangeNotification notification over here: https://devforums.apple.com/message/237718#237718