nodeAtPoint wrong node - ios

Question

I'm making a game with swift and spritekit and I have a function where I have multiple sprites falling from the top of the screen. I also made it so I can be able to detect a touch on the sprite using nodeAtPoint, and made it possible to flick the sprites. My problem is that due to nodeAtPoint dragging the deepest node in the tree, when i click and drag on a sprite, the newest sprite in the scene gets pulled toward my touch instead of the one i originally touched. If anyone has some suggestions on how to only affect the node I touched I'd really appreciate it.
class GameScene: SKScene {
var ball = SKSpriteNode(imagedNamed: "blueBlue")
var touchedNode: SKNode? = SKNode()
override func didMoveToView(view: SKView) {
var create = SKAction.runBlock({() in self.createTargets()})
var wait = SKAction.waitForDuration(2)
var waitAndCreateForever = SKAction.repeatActionForever(SKAction.sequence([create, wait]))
self.runAction(waitAndCreateForever)
}
func createTargets() {
ball = SKSpriteNode(imageNamed: "blueBlue")
let randomx = Int(arc4random_uniform(170) + 290)
ball.zPosition = 0
ball.physicsBody = SKPhysicsBody(circleOfRadius: ball.size.width / 11)
ball.physicsBody?.dynamic = true
ball.size = CGSize(width: ball.size.width / 1.5, height: ball.size.height / 1.5)
let random = Int(arc4random_uniform(35))
let textures = [texture1, texture2, texture3, texture4, texture5, texture6, texture7, texture8, texture9, texture10, texture11, texture12, texture13, texture14, texture15, texture16, texture17, texture18, texture19, texture20, texture21, texture22, texture23, texture24, texture25, texture1, texture7, texture18, texture24, texture25, texture1, texture7, texture18, texture24, texture25]
ball.texture = textures[random]
ball.position = CGPoint(x: randomx, y: 1400)
addChild(ball)
}
override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
let touch = touches.first as! UITouch
let touchLocation = touch.locationInNode(self)
touchedNode = self.nodeAtPoint(touchLocation)
if touchedNode.frame.contains(touchLocation) {
touching = true
touchPoint = touchLocation
}
}
override func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
let touch = touches.first as! UITouch
let touchLocation = touch.locationInNode(self)
touching = true
touchPoint = touchLocation
}
override func update(currentTime: NSTimeInterval) {
if touching {
if touchPoint != touchedNode.position {
let dt: CGFloat = 0.1
let distance = CGVector(dx: touchPoint.x - touchedNode.position.x, dy: touchPoint.y - touchedNode.position.y)
let vel = CGVector(dx: distance.dx / dt, dy: distance.dy / dt)
if touchedNode.parent != nil {
touchedNode.physicsBody?.velocity = vel
}
}
}
}
}

Answer 1

I suggest you make the following changes to the code:
Add a check to see if a sprite is already being moved (if yes, do nothing)
Turn off the affectedByGravity property for the sprite being moved
Reset touchedNode and touching variables when the touch ends
Here's an implementation with the above changes...
Replace touchesBegan and touchesMoved with the following
override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
let touch = touches.first as! UITouch
let touchLocation = touch.locationInNode(self)
if (!touching) {
let node = self.nodeAtPoint(touchLocation)
if node is SKSpriteNode {
touchedNode = node
touching = true
touchPoint = touchLocation
touchedNode!.physicsBody?.affectedByGravity = false
}
}
}
override func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
if (touching) {
let touch = touches.first as! UITouch
let touchLocation = touch.locationInNode(self)
touchPoint = touchLocation
}
}
And add this method
override func touchesEnded(touches: Set<NSObject>, withEvent event: UIEvent) {
if (touchedNode != nil) {
touchedNode!.physicsBody!.affectedByGravity = true
}
touchedNode = nil
touching = false
}