Swift, Spritekit Rotating sprites swift 3 - ios

Question

I am trying to rotate a sprite using swift, IOS 10 and the touchesmoved function, the code I have works in the fact it moves the sprite but in not the right way, the wrong directions etc.
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
super.touchesMoved(touches, with: event)
guard let touch=touches.first{
return
}
let touchLocation = touch.location(in: self)
self.zRotation=CGFloat(atan2(Double(touchLocation.y), Double(touchLocation.x)))
}
does anyone know the correct way to rotate a sprite using zRotation and touchesMoved?
Thank you

Answer 1

I think you've probably overlooked the wonderful power of constraints in SpriteKit. Easy enough to do, Apple does a terrible job of promoting, presenting and educating those considering using SpriteKit.
Constraints allow you to say "go here", or "look at this".
In your case, the "look at this" is ideal, from the docs:
Orientation Constraints
A common use for orientation constraints is to make a look-at
constraint. For example, you may create a look-at constraint to make a
pair of eyes follow a moving object or to have a rocket point in the
direction of its target.
More specifically, you can use these in your touchesMoved:
https://developer.apple.com/reference/spritekit/skconstraint/1519627-orient

Answer 2

thanks for all the suggestions. Yes my explanation of the problem was not too great. so will add the full code here and it seems to be working apart from occasionally moving by 90 degrees on its own when i stop dragging and start dragging again
What I was trying to do was rotate a sprite around another sprite for example a cannon barrel around its wheel... When the wheel is loaded from the scene it calls this class and adds a child node (the barrel) which should be able to be moved around its wheel
import SpriteKit
class WheelNode: SKSpriteNode, CustomNodeEvent{
private var tubeNode=SKSpriteNode(imageNamed: "cannon-barrel")
var previousPoint:CGPoint!
var touchLocation:CGPoint!
func didMoveToScene() {
guard let scene=scene else{
return
}
isUserInteractionEnabled=true
tubeNode.anchorPoint=CGPoint(x:0, y:0)
tubeNode.position=position
self.addChild(tubeNode)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
if let touch=touches.first{
previousPoint=touch.location(in: scene!)
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
super.touchesMoved(touches, with: event)
if let touch=touches.first{
touchLocation=touch.location(in: scene!)
var angle=atan2(touchLocation.y-previousPoint.y, touchLocation.x-previousPoint.x)
self.zRotation=angle
}
}
}