Adding a collision to a UIView with a pangesture with Swift

Question

I'm trying to make a pong game in Xcode without using the Spritekit. I'm using UIVeiws for the ball and paddles. To move the paddle I used a pan gesture recognizer in the storyboard and connected it to the UIView.

I want to add a collision to the paddle, but I need it to move with the paddle. Right now, with the addBoundaryWithIdentifier, it only works when the paddle is at origin.

Help help! Here's my code so far...

class ViewController: UIViewController, UICollisionBehaviorDelegate {

var animator = UIDynamicAnimator()
var collision: UICollisionBehavior!
var paddleOneOriginalCenter: CGPoint!

@IBOutlet weak var ball: UIImageView!
@IBOutlet weak var paddleOne: UIView!

@IBAction func panGesturePaddleOne(sender: UIPanGestureRecognizer) {
    let translation = sender.translationInView(view)
    if sender.state == UIGestureRecognizerState.Began {
        paddleOneOriginalCenter = paddleOne.center
    }
    paddleOne.center.y = paddleOneOriginalCenter.y + translation.y
}

override func viewDidLoad() {
    super.viewDidLoad()

    // Set up ball Dynamic Behaviors
    self.animator = UIDynamicAnimator(referenceView: self.view)

    // Ball Collisions
    collision = UICollisionBehavior(items: [ball])
    collision.addBoundaryWithIdentifier("paddleOne", forPath: UIBezierPath(rect: paddleOne.frame))

    collision.setTranslatesReferenceBoundsIntoBoundaryWithInsets(UIEdgeInsets(top: 10, left: 1000, bottom: 10, right: 1000))
    animator.addBehavior(collision)

    // Ball Initial Velocity (Puhs)
    var pushBehavior: UIPushBehavior = UIPushBehavior(items:[ball], mode: UIPushBehaviorMode.Instantaneous)
    pushBehavior.pushDirection = getRandomDirection()
    pushBehavior.magnitude = 1
    animator.addBehavior(pushBehavior)

    // Ball Bounce
    let bounceBehaviour = UIDynamicItemBehavior(items: [ball])
    bounceBehaviour.elasticity = 1.1
    animator.addBehavior(bounceBehaviour)
}

func getRandomDirection() -> CGVector {
    let x = CGFloat(arc4random())
    let y = CGFloat(arc4random())
    return CGVectorMake(x, y)
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}

Answer 1

I handled the situation by making the paddle very, very heavy to offset the collision with the ball. It's probably not the prettiest solution, but it works!

@IBAction func panGesturePaddleOne(sender: UIPanGestureRecognizer) {
    let translation = sender.translationInView(view)
    if sender.state == UIGestureRecognizerState.Began {
        paddleOneOriginalCenter = paddleOne.center
    }
    paddleOne.center.y = paddleOneOriginalCenter.y + translation.y
    self.animator.updateItemUsingCurrentState(paddleOne)
}

override func viewDidLoad() {
    super.viewDidLoad()

    // Set up ball Dynamic Behaviors
    self.animator = UIDynamicAnimator(referenceView: self.view)


    //Make paddle heavy
    let paddleDynamicProperties = UIDynamicItemBehavior(items: [paddleOne, paddleTwo])
    paddleDynamicProperties.density = 10000000
    paddleDynamicProperties.allowsRotation = false
    animator.addBehavior(paddleDynamicProperties)

    // Ball Collisions
    collision = UICollisionBehavior(items: [ball, paddleOne, paddleTwo])
    collision.setTranslatesReferenceBoundsIntoBoundaryWithInsets(UIEdgeInsets(top: 10, left: 1000, bottom: 10, right: 1000))
    animator.addBehavior(collision)
    self.collision.addBoundaryWithIdentifier("left", fromPoint: CGPointMake(0, 0), toPoint: CGPointMake(0, self.view.frame.size.height))
     self.collision.addBoundaryWithIdentifier("right", fromPoint: CGPointMake(self.view.frame.size.width, 0), toPoint: CGPointMake(self.view.frame.size.width, self.view.frame.size.height))

    collision.collisionDelegate = self

    // Ball Initial Velocity (Push)
    pushBall()

    // Ball Bounce
    let bounceBehaviour = UIDynamicItemBehavior(items: [ball])
    bounceBehaviour.elasticity = 1.0
    bounceBehaviour.friction = 0
    bounceBehaviour.resistance = 0
    animator.addBehavior(bounceBehaviour)
}