Line drawing with SKShapeNode

Question

I want to just draw a string using SKShapeNode. I use SpriteKit and Swift.

Here is my code:

var line = SKShapeNode()
var ref = CGPathCreateMutable()

    override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {

    for touch: AnyObject in touches {
        let location = touch.locationInNode(self)

    }
}

override func touchesMoved(touches: NSSet, withEvent event: UIEvent) {

    for touch: AnyObject in touches {
        let locationInScene = touch.locationInNode(self)

        CGPathMoveToPoint(ref, nil, locationInScene.x, locationInScene.y)
        CGPathAddLineToPoint(ref, nil, locationInScene.x, locationInScene.y)
        line.path = ref
        line.lineWidth = 4
        line.fillColor = UIColor.redColor()
        line.strokeColor = UIColor.redColor()
        self.addChild(line)

    }
}

Whenever I run it and try to draw a line, the application crashes with an error: Reason: 'Accepted to add SKNode, which already has a parent: SKShapeNode name:' (null) 'accumulatedFrame: {{0, 0}, {0 , 0}} '

Why is this happening?

Answer 1

Ok, you add the same child instance again and again. Create a node string every time and every time add it to the parent node, then it will solve your problem.

var ref = CGPathCreateMutable()

override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {

    if let touch = touches.anyObject() as? UITouch {
        let location = touch.locationInNode(self)
        CGPathMoveToPoint(ref, nil, location.x, location.y)
    }
}

override func touchesMoved(touches: NSSet, withEvent event: UIEvent) {

    for touch: AnyObject in touches {
        let locationInScene = touch.locationInNode(self)
        var line = SKShapeNode()
        CGPathAddLineToPoint(ref, nil, locationInScene.x, locationInScene.y)
        line.path = ref
        line.lineWidth = 4
        line.fillColor = UIColor.redColor()
        line.strokeColor = UIColor.redColor()
        self.addChild(line)
    }
}