How to run functions on different threads?

Question

I need the functions below to run on different threads. I think I have to use a concurrent dispatch queue, but i'm not sure how to do that so I was hoping for some help!

First function:

func respondToSwipeGesture(sender: UISwipeGestureRecognizer) {

            switch sender.direction {
        case UISwipeGestureRecognizerDirection.Left:
            if self.imageView.tag == 1 {
                println("1 point!")
            } else {
                if self.imageView.tag == 5 {
                    println("1 point!")
                } else {
                    println("Game Over!")
                }
            }
        case UISwipeGestureRecognizerDirection.Down:
            if self.imageView.tag == 2 {
                println("1 point!")
            } else {
                if self.imageView.tag == 8 {
                    println("1 point!")
                } else {
                    println("Game Over!")
                }
            }
        case UISwipeGestureRecognizerDirection.Right:
            if self.imageView.tag == 3 {
                println("1 point!")
            } else {
                if self.imageView.tag == 7 {
                    println("1 point!")
                } else {
                    println("Game Over!")
                }
            }
        case UISwipeGestureRecognizerDirection.Up:
            if self.imageView.tag == 4 {
                println("1 point!")
            } else {
                if self.imageView.tag == 6 {
                    println("1 point!")
                } else {
                    println("Game Over!")
                }
            }
        default:
            break
        }

Second function:

 @IBAction func handleAttachmentGesture(sender: UIPanGestureRecognizer) {
    let location = sender.locationInView(self.view)
    let boxLocation = sender.locationInView(self.imageView)

    switch sender.state {
    case .Began:
      println("Your touch start position is \(location)")
      println("Start location in image is \(boxLocation)")

      // 1
      animator.removeAllBehaviors()

      // 2
      let centerOffset = UIOffset(horizontal: boxLocation.x - imageView.bounds.midX,
        vertical: boxLocation.y - imageView.bounds.midY)
      attachmentBehavior = UIAttachmentBehavior(item: imageView,
        offsetFromCenter: centerOffset, attachedToAnchor: location)

      // 3
      redSquare.center = attachmentBehavior.anchorPoint
      blueSquare.center = location

      // 4
      animator.addBehavior(attachmentBehavior)

    case .Ended:
      println("Your touch end position is \(location)")
      println("End location in image is \(boxLocation)")

      animator.removeAllBehaviors()

      // 1
      let velocity = sender.velocityInView(view)
      let magnitude = sqrt((velocity.x * velocity.x) + (velocity.y * velocity.y))

      if magnitude > ThrowingThreshold {
        // 2
        let pushBehavior = UIPushBehavior(items: [imageView], mode: .Instantaneous)
        pushBehavior.pushDirection = CGVector(dx: velocity.x / 10, dy: velocity.y / 10)
        pushBehavior.magnitude = magnitude / ThrowingVelocityPadding

        self.pushBehavior = pushBehavior
        animator.addBehavior(pushBehavior)

        // 3
        let angle = Int(arc4random_uniform(20)) - 10

        itemBehavior = UIDynamicItemBehavior(items: [imageView])
        itemBehavior.friction = 0.2
        itemBehavior.allowsRotation = true
        itemBehavior.addAngularVelocity(CGFloat(angle), forItem: imageView)
        animator.addBehavior(itemBehavior)

        // 4
        let timeOffset = Int64(0.4 * Double(NSEC_PER_SEC))
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, timeOffset), dispatch_get_main_queue()) {
            self.resetDemo()
        }
      } else {
        resetDemo()
        }

    default:
        attachmentBehavior.anchorPoint = sender.locationInView(view)
        redSquare.center = attachmentBehavior.anchorPoint
    }

Answer 1

Not sure what you're trying to do (haven't read the whole code). But still, if you are sure you need to run on different queue, here is a quick example that might help you :

let aCustomQueue = dispatch_queue_create("aCustomQueueLabel", DISPATCH_QUEUE_CONCURRENT)
let anotherCustomQueue = dispatch_queue_create("anotherCustomQueueLabel", DISPATCH_QUEUE_CONCURRENT)

dispatch_async(aCustomQueue) {

    for _ in 0...1000 {
        NSLog("Hello") // println("Hello") will print char by char
    }
}


dispatch_async(anotherCustomQueue) {

    for _ in 0...1000 {
        NSLog("World") // println("World") will print char by char
    }

}

Otherwise, you might want to give a look at :

• Grand Central Dispatch (GCD) Reference : https://developer.apple.com/library/prerelease/ios/documentation/Performance/Reference/GCD_libdispatch_Ref/index.html#//apple_ref/c/func/dispatch_get_main_queue
• Ray Wenderlich GCD : http://www.raywenderlich.com/79149/grand-central-dispatch-tutorial-swift-part-1