     private static let timerRunLoop = NSRunLoop.currentRunLoop()
     private static let timerPort = NSPort()
     
+    deinit {
+        NSNotificationCenter.defaultCenter().removeObserver(self, name: UIApplicationWillEnterForegroundNotification, object: nil)
+    }
+    
     public override class func initialize() {
         super.initialize()
         

    private func lotateAnimation(duration: CFTimeInterval) -> CAPropertyAnimation {
        let anim = CABasicAnimation(keyPath: "transform.rotation.z")
        anim.duration = duration
        anim.repeatCount = 1
        anim.fromValue = -(M_PI + M_PI_4)
        anim.toValue = M_PI - M_PI_4
        


// MARK: - Timer
internal extension SpringIndicator {
    private func createStrokeTimer(timeInterval ti: NSTimeInterval, userInfo: AnyObject?, repeats yesOrNo: Bool) -> NSTimer {
        return NSTimer(timeInterval: ti, target: self, selector: Selector("onStrokeTimer:"), userInfo: userInfo, repeats: yesOrNo)
    }
