 
 final class Waver: UIView {
     
-    var displayLink: CADisplayLink!
+    var displayLink: CADisplayLink?
     
     var numberOfWaves: Int = 5
     

    }

    deinit {
        displayLink.invalidate()
    }
    
    required init?(coder aDecoder: NSCoder) {


    var waverCallback: ((waver: Waver) -> ())? {
        didSet {
            displayLink?.invalidate()
            displayLink = CADisplayLink(target: self, selector: #selector(Waver.callbackWaver))
            displayLink?.addToRunLoop(NSRunLoop.currentRunLoop(), forMode: NSRunLoopCommonModes)
            
            (0..<self.numberOfWaves).forEach { i in
                let waveline = CAShapeLayer()
