Call function when if value in NSUserDefaults.standardUserDefaults() changes

Question

I have a variable that become value from NSUserDefaults.standardUserDefaults()

var GiftCount = NSUserDefaults.standardUserDefaults().valueForKey("Gift") as! Int

And i have a function named setGiftCount()...

I need call this function when variable GiftCount has changed... How to do it?

Answer 1

First

NSUserDefaults.standardUserDefaults().addObserver(self, forKeyPath: "Gift", options: NSKeyValueObservingOptions.New, context: nil)

Second

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

Third

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
    setGiftCount()
}