Nodes in SKShapeNode reappearing when creating another new node - ios

Question

Im trying to write the code for a line that draws with the drag of a finger but deletes when the finger is removed (in SpriteKit and Swift 3)
var shapeNodes = [SKShapeNode]()
var pathToDraw = CGMutablePath()
var lineNode = SKShapeNode()
func deleteAllShapeNodes() {
for node in shapeNodes {
node.removeFromParent()
}
shapeNodes.removeAll(keepingCapacity: false)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch: AnyObject in touches {
firstPoint = touch.location(in: self)
}
shapeNodes.append(lineNode)
pathToDraw.move(to: CGPoint(x: firstPoint.x, y: firstPoint.y))
lineNode.lineWidth = 4
lineNode.strokeColor = UIColor.white
lineNode.name = "Line"
lineNode.zPosition = 100000
lineNode.path = pathToDraw
self.addChild(lineNode)
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch: AnyObject in touches{
positionInScene = touch.location(in: self)
}
shapeNodes.append(lineNode)
pathToDraw.addLine(to: CGPoint(x: positionInScene.x, y: positionInScene.y))
lineNode.path = pathToDraw
firstPoint = positionInScene
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch: AnyObject in touches{
TouchEndPosition = touch.location(in: self)
}
self.deleteAllShapeNodes()
}
the first line draws and deletes perfectly but when i start drawing the second line the first line reappears.

Answer 1

Creating a brand-new CGMutablePath seems to be the only way to get an empty CGMutablePath.
And you are adding the only instance of SKShapeNode (kept in lineNode) into shapeNodes, it's non-sense. Your lineNode keeps all the lines you added to your pathToDraw.
Generally, you may need to learn when to instantiate objects, and when to release them.
Try this:
//### You are adding the same instance multiple times into this array, it's nonsense.
//var shapeNodes = [SKShapeNode]()
//### `pathToDraw` can be kept in the `SKShapeNode`.
//var pathToDraw = CGMutablePath()
//### In this case, this is not a good place to instantiate an `SKShapeNode`.
var lineNode: SKShapeNode?
func deleteAllShapeNodes() {
//### Release the `SKShapeNode` contained in `lineNode` to delete all lines.
lineNode?.removeFromParent()
lineNode = nil
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
let firstPoint = touches.first!.location(in: self)
self.lineNode?.removeFromParent()
//### If you want somethings which live while dragging, `touchesBegan(_:with:)` is a good place to instantiate them.
let lineNode = SKShapeNode()
//### Create an empty new `CGMutablePath` at each `touchesBegan(_:with:)`.
let pathToDraw = CGMutablePath()
self.lineNode = lineNode
pathToDraw.move(to: firstPoint)
lineNode.lineWidth = 4
lineNode.strokeColor = UIColor.white
lineNode.name = "Line"
lineNode.zPosition = 100000
//### `pathToDraw` is kept in the `SKShapeNode`.
lineNode.path = pathToDraw
self.addChild(lineNode)
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
let positionInScene = touches.first!.location(in: self)
if let lineNode = self.lineNode {
//### Modify the `CGMutablePath` kept in the `SKShapeNode`.
let pathToDraw = lineNode.path as! CGMutablePath
pathToDraw.addLine(to: positionInScene)
//### Refresh the shape of the `SKShapeNode`.
lineNode.path = pathToDraw
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
self.deleteAllShapeNodes()
}