SKPhysicsContactDelegate didBegin将无法运行

Question

我正在使用SpriteKit创建一个Swift Playground但无法使碰撞检测工作。我已经在StackOverFlow上阅读了有关此问题的所有帖子，但没有一个帖子解决了我的问题。以下是我的代码：

public class MyScene: SKScene, SKPhysicsContactDelegate {    

var node: SKSpriteNode?

var touchedNodeCreator: Timer?

let nodeCategory : UInt32 = 0x1 << 1

let touchedNodeCategory : UInt32 = 0x1 << 2

var score = 0

public override func didMove(to view: SKView) {

    //Setup

    physicsWorld.contactDelegate = self

    self.backgroundColor =
        UIColor(red:0.60, green:0.88, blue:1.00, alpha:1.0)

    //node

    node = SKSpriteNode(imageNamed: "node")

    node!.setScale(0.175)

    node!.physicsBody? = SKPhysicsBody(rectangleOf: node!.size)

    node!.physicsBody?.categoryBitMask = nodeCategory

    node!.physicsBody?.contactTestBitMask = touchedNodeCategory

    node!.physicsBody?.collisionBitMask = floorCategory

    floor.physicsBody?.categoryBitMask = floorCategory

    floor.physicsBody?.collisionBitMask = nodeCategory

    let nodeStartingPos = CGPoint(x: node!.size.width / 2 + 25, y: self.size.height / 5 + node!.size.height / 2)

    node!.position = nodeStartingPos

    addChild(node!)

    //Create touchedNode Timer

    touchedNodeCreator = Timer.scheduledTimer(withTimeInterval: 3, repeats: true) { (timer) in
        self.createtouchedNode()
    }

}

func createtouchedNode() {

    let touchedNode = SKSpriteNode(imageNamed: "otherNode")

    touchedNode.setScale(0.2)

    touchedNode.name = "TouchedNode"

    touchedNode.physicsBody? = SKPhysicsBody(rectangleOf: touchedNode.size)

    touchedNode.physicsBody?.affectedByGravity = false

    let maxY = self.size.height / 1 - touchedNode.size.height / 2

    let minY = self.size.height / 5 + 25

    let rangeY = maxY - minY

    let y = maxY - CGFloat(arc4random_uniform(UInt32(rangeY)))

    let touchedNodeStartingPos = CGPoint(x: self.size.width + 20, y: y)

    touchedNode.position = touchedNodeStartingPos

    touchedNode.physicsBody?.categoryBitMask = touchedNodeCategory

    touchedNode.physicsBody?.contactTestBitMask = nodeCategory

    addChild(touchedNode)

    let moveLeft = SKAction.moveBy(x: -size.width - touchedNode.size.width, y: 0, duration: 3)

    let remove = SKAction.removeFromParent()

    let sequence = SKAction.sequence([moveLeft, remove])

    touchedNode.run(sequence)

}

public func didBegin(_ contact: SKPhysicsContact) {

    print("Began")

    if contact.bodyA.categoryBitMask == touchedNodeCategory {

        contact.bodyA.node?.removeFromParent()

        score += 1

        print(score)

    } else if contact.bodyB.categoryBitMask == touchedNodeCategory {

        contact.bodyB.node?.removeFromParent()

        score += 1

        print(score)

    }

}

请记住，我省略了很多代码，主要是在检测到任何触摸时移动节点的代码。

如果你们能帮我解决这个问题，我将不胜感激。谢谢！