make SKPhysicsBody unidirectional - ios

Question

I have a SKSpriteNode as a ball, it's been given all the SKPhysicsBody properties move around in all direction. What I want now is to make it unidirectional (only move in that direction it hasn't move to before and not go back in to a path it had move upon). Currently I have following thoughts on this the problem,
make a fieldBitMask, to the path that is iterated by it and repel
the ball to not go back
apply some kind of force/ impulses on the ball from touchesBegan/ touchesMoved method to keep it from going back
something that can be handled in update method
a lifesaver from stackflowoverflow, who is coding even on the weekend :)
Supporting Code snippets for better understanding,
//getting current touch position by using UIEvent methods
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
guard let touch = touches.first else {return}
let location = touch.location(in: self)
lastTouchPoint = location
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
guard let touch = touches.first else {return}
let location = touch.location(in: self)
lastTouchPoint = location
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
lastTouchPoint = nil
}
override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
lastTouchPoint = nil
}
//ball created
func createPlayer(){
player = SKSpriteNode(imageNamed: "player")
player.position = CGPoint(x: 220, y: 420)
player.zPosition = 1
//physics for ball
player.physicsBody = SKPhysicsBody(circleOfRadius: player.size.width / 2)
player.physicsBody?.allowsRotation = false
player.physicsBody?.linearDamping = 0.5
player.physicsBody?.categoryBitMask = collisionTypes.player.rawValue
player.physicsBody?.contactTestBitMask = collisionTypes.finish.rawValue
player.physicsBody?.collisionBitMask = collisionTypes.wall.rawValue
addChild(player)
}
//unwarp the optional property, calclulate the postion between player touch and current ball position
override func update(_ currentTime: TimeInterval) {
guard isGameOver == false else { return }
if let lastTouchPosition = lastTouchPoint {
//this usually gives a large value (related to screen size of the device) so /100 to normalize it
let diff = CGPoint(x: lastTouchPosition.x - player.position.x, y: lastTouchPosition.y - player.position.y)
physicsWorld.gravity = CGVector(dx: diff.x/100, dy: diff.y/100)
}
}

Answer 1

Well it was a combination little hacks in touchesBegan/ touchesMoved and update func,
First you need to catch on which touch occurred, get it's name (in my
case I made nodes which had alpha of 0, but become visible upon
moving over them i.e alpha 1). In touchesBegan, touchesMoved as follow
guard let touch = touches.first else {return}
let location = touch.location(in: self)
lastTouchPoint = location
let positionInScene = touch.location(in: self)
let touchedNode = self.atPoint(positionInScene)
if let name = touchedNode.name
{
if name == "vortex"
{
touching = false
self.view!.isUserInteractionEnabled = false
print("Touched on the interacted node")
}else{
self.view!.isUserInteractionEnabled = true
touching = true
}
}
}
Second use a BOOL touching to track user interactions, on the screen by using getting a tap recogniser setup, as follow
func setupTapDetection() {
let t = UITapGestureRecognizer(target: self, action: #selector(tapped(_:)))
view?.addGestureRecognizer(t)
}
#objc func tapped(_ tap: UITapGestureRecognizer) {
touching = true
}
Finally in update put checks as follow,
guard isGameOver == false else { return }
self.view!.isUserInteractionEnabled = true
if(touching ?? true){
if let lastTouchPosition = lastTouchPoint {
//this usually gives a large value (related to screen size of the device) so /100 to normalize it
let diff = CGPoint(x: lastTouchPosition.x - player.position.x, y: lastTouchPosition.y - player.position.y)
physicsWorld.gravity = CGVector(dx: diff.x/100, dy: diff.y/100)
}
}
}