ios - 通过触摸在枚举状态之间切换

Question

我有一个像这样的简单播放器类:

enum State: Int {

   case dead, alive, idle

    }

class Player {

    var playerSprite : SKSpriteNode
    var currentState : State


init(passedInState: State) {

    currentState = passedInState
    self.playerSprite = SKSpriteNode(imageNamed: "playersprite.png")

    switch currentState {

        case .dead:
            println("Player is dead")

        case .alive:
            println("Player is alive")

       }

  }
 }

在我的主类中，我创建了一个 Player 类的实例，并尝试通过在 touch 方法中点击它来更改玩家状态，如下所示:

class GameScene: SKScene {
    override func didMoveToView(view: SKView) {

        let player1 = Player(passedInState: .alive)
        self.addChild(player1.playerSprite)
        player1.playerSprite.position = CGPointMake(100, 100)
}


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

        let touch = touches.anyObject() as UITouch
        let location = touch.locationInNode(self)
        var locationSprites = nodesAtPoint(location)

        for bla in locationSprites {

        (bla as Player).currentState = .dead

        }
    }
}

我在触摸 Sprite 时总是崩溃。你知道为什么吗？

Answer 1

似乎有一个沮丧的失败，在你的代码中我看到有 2 个强制的 donwcasts:

let touch = touches.anyObject() as UITouch

和

(bla as Player).currentState = .dead

我假设错误在最后一个，所以我建议设置一个断点并检查 bla 以检查它是否实际上是 Player 的实例。根据您的逻辑，如果它可能不是 Player 的实例，我建议使用可选的向下转换:

if let player = bla as? Player {
    player.currentState = .dead
}

优点是如果 bla 不是 Player 的实例，则不会执行 if block ，而不是使应用程序崩溃。

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评论跟进

如果想在播放器状态变化时做一些自定义处理，可以在Player类的currentState属性中添加一个属性观察器:

var currentState : State {
    didSet {
        switch currentState {                
        case .dead:
            println("Player is dead")

        case .alive:
            println("Player is alive")

        case .idle:
            break
        }
    }
}