Bouncy UIButton in swift. Becomes small when pressed and restores its size when released. Swift 2

BouncyButton.swift

//
//  BouncyButton.swift
//
//  Created by Domink Felber on 20.03.16.
//  Copyright © 2016 Domink Felber. All rights reserved.
//

import Foundation
import UIKit


class BouncyButton: UIButton
{
    override func beginTrackingWithTouch(touch: UITouch, withEvent event: UIEvent?) -> Bool {
        let ret = super.beginTrackingWithTouch(touch, withEvent: event)
        
        if ret {
            onTouchDown()
        }
        
        return ret
    }
    
    
    override func endTrackingWithTouch(touch: UITouch?, withEvent event: UIEvent?)
    {
        onTouchUp()
        return super.endTrackingWithTouch(touch, withEvent: event)
    }
    
    
    override func cancelTrackingWithEvent(event: UIEvent?)
    {
        onTouchUp()
        return super.cancelTrackingWithEvent(event)
    }
    
    
    func onTouchDown()
    {
        UIView.animateWithDuration(1.2,
            delay: 0.0,
            usingSpringWithDamping: 0.2,
            initialSpringVelocity: 6.0,
            options: UIViewAnimationOptions.AllowUserInteraction,
            animations: { () -> Void in
                self.transform = CGAffineTransformMakeScale(0.6, 0.6)
            }, completion: nil)
    }
    
    
    func onTouchUp()
    {
        UIView.animateWithDuration(1.2,
            delay: 0.0,
            usingSpringWithDamping: 0.2,
            initialSpringVelocity: 6.0,
            options: UIViewAnimationOptions.AllowUserInteraction,
            animations: { () -> Void in
                self.transform = CGAffineTransformMakeScale(1.0, 1.0)
            }, completion: nil)
    }
}