iOS NSUserDefaults Watching the change of values for a single key

Question

I have the following code aiming to catch the event of a NSUserDefaults value changing for a particular key.

 [[NSUserDefaults standardUserDefaults] addObse         


        

Answer 1

Swift Version:

func setUserDefaultsListener(){
    NSUserDefaults.standardUserDefaults().addObserver(self, forKeyPath: "keyPath", options: NSKeyValueObservingOptions.New, context: nil)
}

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer) {
    if keyPath == "keyPath" {
        //Do something
    }
}

deinit {
    NSUserDefaults.standardUserDefaults().removeObserver(self, forKeyPath: "keyPath")
}