我的物理联系人没有在SpriteKit中联系

这是我在堆栈上发布的第一个问题 . 我正在使用Xcode 7.3.1，iOS 9.3和Swift 2.还在模拟器和我的iPad上直接测试 . 我做了大量的搜索，阅读了2本Spritekit Physics书籍，观看了大量的视频教程以及书面教程 . 我以前写的身体物理没有问题，而且很多时候都有较小的项目，但这个只是给我没有反馈 . 这个问题之前已在特定情况下提出过，即2次与同一spritenode的碰撞或者collisionBitMask和contactTestBitMask之间的区别是什么 . 我知道这些差异并且还意识到您希望联系的每个对象都需要categoryBitMask . 首先，我已经分配了一个全局的Physicsbody结构（尝试直接二进制bitMask和相应的Int32，每个对应的Int32都没有成功），物理代表和每个SKSpritenode对应其配对的联系人 . 我已经尝试了很多方法来实现didBeginContact（关于它的结构方式），没有一种方法可以与另一方面有所区别 .
之前我提到了反馈 . 除了我的主要球员，子弹，新敌人和敌人之外，我已经淘汰了所有人 . 当我尝试将接触或碰撞的结果打印到控制台时，就好像它甚至无法读取 . 我没有活动 . 这些spritenode都在1级（GameScene）中，我已经为每个功能spritenode尝试了单独的类，没有运气 . 此外，对于单独的类，它似乎会使事情变得更糟，即使有用于在类和子类之间进行通信的协议 . 哪些使用单独的类对我来说仍然是新的，尽管我知道它是首选的方式 . 我将只展示我认为可能需要被视为最小化的代码，但如果还有其他需要被看到的话，请告诉我 . 我只是希望子弹击中飞机，我可以从那里到我的其他物体 .

import AVFoundation
import SpriteKit
import GameKit

// Binary connections for collision and colliding
struct PhysicsCategory {
    static let GroundMask : UInt32 = 1    //0x1 << 0
    static let BulletMask : UInt32 = 2    //0x1 << 1
    static let PlayerMask : UInt32 = 4    //0x1 << 2
    static let EnemyMask  : UInt32 = 8    //0x1 << 3
    static let EnemyFire  : UInt32 = 16   //0x1 << 4
    static let All        : UInt32 = UInt32.max // all nodes
}

class GameScene: SKScene, SKPhysicsContactDelegate {

    // Starting scene, passed to didMoveToView
    func startScene() {

        // Sets the physics delegate and physics body
        view?.showsPhysics = true
        self.physicsWorld.gravity = CGVectorMake(0, 0)
        self.physicsBody = SKPhysicsBody(edgeLoopFromRect: self.frame)
        self.physicsWorld.contactDelegate = self // Physics delegate set
    }

    func setupPlayer() {

        player = SKScene(fileNamed: "Player")!.childNodeWithName("player")! as! SKSpriteNode

        // Body physics for player's planes
        player.physicsBody = SKPhysicsBody(texture: SKTexture(imageNamed: "MyFokker2.png"), size: player.size)
        player.physicsBody?.dynamic = false
        player.physicsBody?.usesPreciseCollisionDetection = true
        player.physicsBody?.categoryBitMask = PhysicsCategory.PlayerMask
        player.physicsBody?.contactTestBitMask = PhysicsCategory.EnemyFire
        player.physicsBody?.collisionBitMask = 0

        player.removeFromParent()
        self.addChild(player) // Add our player to the scene
    }

    // Create the ammo for our plane to fire
    func fireBullets() {

        bullet = SKSpriteNode(imageNamed: "fireBullet")

        // Body physics for plane's bulets
        bullet.physicsBody = SKPhysicsBody(rectangleOfSize: bullet.size)
        bullet.physicsBody?.dynamic = false
        bullet.physicsBody?.usesPreciseCollisionDetection = true
        bullet.physicsBody?.categoryBitMask = PhysicsCategory.BulletMask
        bullet.physicsBody?.contactTestBitMask = PhysicsCategory.EnemyMask
        bullet.physicsBody?.collisionBitMask = 0

        self.addChild(bullet) // Add bullet to the scene
    }

    func spawnEnemyPlanes() {
        let enemy1 = SKScene(fileNamed: "Enemy1")!.childNodeWithName("enemy1")! as! SKSpriteNode
        let enemy2 = SKScene(fileNamed: "Enemy2")!.childNodeWithName("enemy2")! as! SKSpriteNode
        let enemy3 = SKScene(fileNamed: "Enemy3")!.childNodeWithName("enemy3")! as! SKSpriteNode
        let enemy4 = SKScene(fileNamed: "Enemy4")!.childNodeWithName("enemy4")! as! SKSpriteNode

        enemyPlanes = [enemy1, enemy2, enemy3, enemy4]

        // Generate a random index
        let randomIndex = Int(arc4random_uniform(UInt32(enemyPlanes.count)))

        // Get a random enemy
        newEnemy = (enemyPlanes[randomIndex])

        // Added randomEnemy's physics
        newEnemy.physicsBody = SKPhysicsBody(rectangleOfSize: newEnemy.size)
        newEnemy.physicsBody?.dynamic = false
        newEnemy.physicsBody?.usesPreciseCollisionDetection = true
        newEnemy.physicsBody?.categoryBitMask = PhysicsCategory.EnemyMask
        newEnemy.physicsBody?.contactTestBitMask = PhysicsCategory.BulletMask
        newEnemy.physicsBody?.collisionBitMask = 0

        newEnemy.removeFromParent()
        self.addChild(newEnemy)
    }

    func spawnEnemyFire() {

        enemyFire = SKScene(fileNamed: "EnemyFire")!.childNodeWithName("bullet")! as! SKSpriteNode

        enemyFire.removeFromParent()
        self.addChild(enemyFire) // Generate enemy fire

        // Added enemy's fire physics
        enemyFire.physicsBody = SKPhysicsBody(rectangleOfSize: enemyFire.size)
        enemyFire.physicsBody?.dynamic = false
        enemyFire.physicsBody?.usesPreciseCollisionDetection = true
        enemyFire.physicsBody?.categoryBitMask = PhysicsCategory.EnemyFire
        enemyFire.physicsBody?.contactTestBitMask = PhysicsCategory.PlayerMask
        enemyFire.physicsBody?.collisionBitMask = 0
    }

    func didBeginContact(contact: SKPhysicsContact) {

        if !self.gamePaused && !self.gameOver {

            // beginContact constants
            firstBody = contact.bodyA
            secondBody = contact.bodyB

            if (contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask) {    
                firstBody = contact.bodyA
                secondBody = contact.bodyB
            } else {   
                firstBody = contact.bodyB
                secondBody = contact.bodyA
            }

            // Contact statements
            if ((firstBody.categoryBitMask & PhysicsCategory.BulletMask != 0) && (secondBody.categoryBitMask & PhysicsCategory.EnemyMask != 0)) {   
                print("Bullet hit Enemy")
            }
            else if ((firstBody.categoryBitMask & PhysicsCategory.PlayerMask != 0) && (secondBody.categoryBitMask & PhysicsCategory.EnemyFire != 0)) {
                print("EnemyFire hit our Player")
            }
        }
    }
}

我试图忽略明显的代码，但留下需要知道的代码...对不起，如果它很长 . 我也尝试过checkPhysics函数，它们甚至无法识别我的对象 . 所有SpriteNodes都传递给didMoveToView函数 . 任何人都可以看到有什么问题或有理由说我根本没有联系吗？