detect nodes last position - swift

Question

I create an game that include balls that has gravity and restitution properties (every ball has different properties by random function). now I want to detect the last position of each ball and then call a remove from node function. Im using the update function to detected the position of the ball while its jumping on the screen. im not sure if I can and how can I detect its last position. Im thinking about create an array that will store each position but I not sure if its right way and wonder if there is a simpler and better way.
here is my code for now:
override func update(_ currentTime: TimeInterval) {
self.enumerateChildNodes(withName: "BALL") { (node:SKNode, nil) in
print(node.position)
}
}
can you help me with that? the array option is only way or there is another one and better one?

Answer 1

You could subclass the ball and add your own property that stores the position.
class BallNode: SKShapeNode {
var lastPosition: CGPoint?
}
let ball = BallNode()
ball.name = “BALL”
ball.position = CGPoint.zero
self.addChild(ball)
In update....
override func update(_ currentTime: TimeInterval) {
self.enumerateChildNodes(withName: "BALL") { (node:BallNode, nil) in
print(node.position)
if let last= node.lastPosition {
print(last)
// do something with last
}
//Update last position before end of updatE
node.lastPosition = node.position
}
}