[Swift/SpriteKit] Game demo with multiple touch panning gestures

GameScene.swift

//http://stackoverflow.com/questions/31928324/how-to-drag-a-skspritenode-without-touching-it-with-swift/31930669?noredirect=1#comment51852474_31930669

import SpriteKit

class GameScene: SKScene {
    
    var leftShape:ConfinedShape!
    var rightShape:ConfinedShape!
    
    override func didMoveToView(view: SKView) {
        
        let radius:CGFloat = 15.0
        let halfFrameSize = CGSizeMake(frame.width / 2, frame.height)
        
        //creates the shapes to be moved
        leftShape = ConfinedShape(circleOfRadius: radius)
        leftShape.position = CGPointMake(frame.width / 4, frame.midY)
        leftShape.strokeColor = UIColor.blueColor()
        leftShape.bounds = CGRect(origin: CGPointZero, size: halfFrameSize)
        leftShape.zPosition = 1
        addChild(leftShape)
        rightShape = ConfinedShape(circleOfRadius: radius)
        rightShape.position = CGPointMake(frame.width * 3 / 4, frame.midY)
        rightShape.strokeColor = UIColor.redColor()
        rightShape.bounds = CGRect(origin: CGPointMake(frame.midX, frame.minY), size: halfFrameSize)
        rightShape.zPosition = 1
        addChild(rightShape)
        
        let leftBoundsRect = SKShapeNode(rect: leftShape.bounds) //indicates touch area for left node
        leftBoundsRect.fillColor = leftShape.strokeColor
        leftBoundsRect.alpha = 0.1
        addChild(leftBoundsRect)
        
        let rightBoundsRect = SKShapeNode(rect: rightShape.bounds)
        rightBoundsRect.fillColor = rightShape.strokeColor
        rightBoundsRect.alpha = 0.1
        addChild(rightBoundsRect)
        
        //sets up gesture recognizer
        let pan = UIPanGestureRecognizer(target: self, action: "panned:")
        pan.maximumNumberOfTouches = 1
        //view.addGestureRecognizer(pan)
    }
    
    
    override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
        for touch in touches {
            if let touch = touch as? UITouch {
                let location = touch.locationInNode(self) //gets touchlocation within the scene
                
                //detects touch within bounds & makes sure that shape is not already selected / associated with touch
                if leftShape.bounds.contains(location) && leftShape.associatedTouchID == nil {
                    leftShape.associatedTouchID = touch.hashValue                                   //hashvalue = unique identifier of touch
                } else if rightShape.bounds.contains(location) && rightShape.associatedTouchID == nil {
                    rightShape.associatedTouchID = touch.hashValue
                }
            }
        }
    }
    override func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
        for touch in touches {
            if let touch = touch as? UITouch {
                let translate = touch.locationInNode(self) - touch.previousLocationInNode(self)  //calculate delta x and delta y of finger
                if leftShape.associatedTouchID == touch.hashValue {
                    leftShape.setPositionWithinBounds(leftShape.position + CGPointMake(translate.x, 0))  //assign new position to shape
                    leftShape.fillColor = leftShape.strokeColor                                  //simple animation to indicate touch in progress
                } else if rightShape.associatedTouchID == touch.hashValue {
                    rightShape.setPositionWithinBounds(rightShape.position + CGPointMake(translate.x, 0))
                    rightShape.fillColor = rightShape.strokeColor
                }
            }
        }
    }
    override func touchesEnded(touches: Set<NSObject>, withEvent event: UIEvent) {
        for touch in touches {
            if let touch = touch as? UITouch {
                let translate = touch.locationInNode(self) - touch.previousLocationInNode(self)
                if leftShape.associatedTouchID == touch.hashValue {
                    leftShape.associatedTouchID = nil          //when touch has ended, delete association with it from node
                    leftShape.fillColor = SKColor.clearColor()
                } else if rightShape.associatedTouchID == touch.hashValue {
                    rightShape.associatedTouchID = nil
                    rightShape.fillColor = SKColor.clearColor()
                }
            }
        }
    }
}

class ConfinedShape:SKShapeNode {
    var associatedTouchID:Int?
    var bounds:CGRect!
    func setPositionWithinBounds (pos:CGPoint) {
        if let bounds = bounds {                                    //unwrap optional
            let radius = self.frame.width / 2
            if CGRectInset(bounds, radius, 0).contains(pos) {       //check if new position is within bounds, taking radius into account
                self.position = pos                                 //assign new pos
            }
        }
    }
}

//handy little helper functions to easily add up CGPoints coordinates
func +(lhs:CGPoint, rhs:CGPoint) -> CGPoint {
    return CGPointMake(lhs.x + rhs.x, lhs.y + rhs.y)
}
func -(lhs:CGPoint, rhs:CGPoint) -> CGPoint {
    return CGPointMake(lhs.x - rhs.x, lhs.y - rhs.y)
}