ios - Spritekit 游戏崩溃(因为 SKLightNode 线程问题？)

Question

我正在尝试为我的 children 制作一款简单的游戏。我正在尝试实现灯光和发射器节点。然而，游戏在碰撞时崩溃，这应该会导致 gameOverScene。奇怪的是，如果我添加一个刹车点，代码可以正常完成。这是代码:

   override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
            touch = touches.first!
            turnOnLightNode(touch.locationInNode(self))   
        }

        override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
            touch = touches.first!
            turnOnLightNode(touch.locationInNode(self))
    }
        override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
            removeLightNode()
        }
        func removeLightNode(){
            var nodeToRemove = self.childNodeWithName("light")
            while(nodeToRemove != nil && endOfSceneCollision == false) {
                nodeToRemove?.removeFromParent()
                nodeToRemove = self.childNodeWithName("light")
            }
            nodeToRemove = self.childNodeWithName("touchEmitterNode")
            while(nodeToRemove != nil && endOfSceneCollision == false) {
                nodeToRemove?.removeFromParent()
                nodeToRemove = self.childNodeWithName("touchEmitterNode")
            }
        }
        override func touchesCancelled(touches: Set<UITouch>?, withEvent event: UIEvent?) {
            removeLightNode()
        }
        func turnOnLightNode(point: CGPoint){

            removeLightNode()

            light.name = "light"
            light.categoryBitMask = 3
            light.position = point
            light.zPosition = 19.0
            light.falloff = 0.5
            light.enabled = true
            light.lightColor = UIColor(red:  161/255, green: 218/255, blue: 237/255, alpha: 0.5)
            light.shadowColor = UIColor(red:  161/255, green: 218/255, blue: 237/255, alpha: 0.5)
            light.ambientColor = UIColor(red:  220/255, green: 220/255, blue: 220/255, alpha: 0.3)

            addChild(light)

            touchEmitter!.name = "touchEmitterNode"
            touchEmitter!.position = point
            touchEmitter!.zPosition = 100//gameFieldParticlesZPosition
            addChild(touchEmitter!)   
        }

func didBeginContact(contact: SKPhysicsContact) {        
        var ballBody: SKPhysicsBody?
        var lineBody: SKPhysicsBody?
        var collidedBallNode: SKSpriteNode?

        if contact.bodyA.categoryBitMask == 2 && contact.bodyB.categoryBitMask == 1 {
            print("didBeginContactAB")

            lineBody = contact.bodyA
            ballBody = contact.bodyB
            collidedBallNode = contact.bodyB.node as? SKSpriteNode
        }
        if contact.bodyA.categoryBitMask == 1 && contact.bodyB.categoryBitMask == 2 {
            print("didBeginContactBA")

            lineBody = contact.bodyB
            ballBody = contact.bodyA
            collidedBallNode = contact.bodyA.node as? SKSpriteNode
        }
        if contact.bodyA.categoryBitMask == 1 && contact.bodyB.categoryBitMask == 4 {
            //audioController.playSound(electricBounceSound, volume: 1.0)
        }
        if contact.bodyA.categoryBitMask == 4 && contact.bodyB.categoryBitMask == 1 {
            //audioController.playSound(electricBounceSound, volume: 1.0)
        }
        if contact.bodyA.categoryBitMask == 1 && contact.bodyB.categoryBitMask == 1 {
            //audioController.playSound(electricNoiseSound, volume: 1.0)
        }

        if(collidedBallNode != nil){
            gotoGameOverScene(collidedBallNode!)

        }
    }
func gotoGameOverScene(explodingBallNode: SKSpriteNode){
        print("step 1") //IF BREAKPOINT HERE, ALL EXECUTES OK           
        self.runAction(SKAction.waitForDuration(2.5), completion: {
            print("step 2")
            let gameOverScene = GameOverScene(size: self.size) 
            print("step 3")
            self.view?.presentScene(gameOverScene, transition: reveal)
            print("step 4")
        })
    }

结果是这样的:

    didBeginContactAB
    step 1
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Attemped to add a SKNode which already has a parent: <SKLightNode> name:'light' position:{296.99994, 191.49995} scale:{1.00, 1.00} accumulatedFrame:{{297, 191.5}, {0, 0}}'
    *** First throw call stack:
    (
        0   CoreFoundation                      0x01384a14 __exceptionPreprocess + 180
        1   libobjc.A.dylib                     0x00b5de02 objc_exception_throw + 50
        2   CoreFoundation                      0x0138493d +[NSException raise:format:] + 141

但是如果我在以下行之前放置调试器断点:

print("step 1")

代码成功执行。一定是线程/同步问题，但这胜过我对 Spritekit/Swift 的专业知识。有人可以帮我解决这个问题吗？

Answer 1

啊……我明白了。 removeLightNode 函数中的一段愚蠢代码。这导致碰撞后移除不起作用:while(nodeToRemove != nil && endOfSceneCollision == false)