SpriteKit游戏开发 Challenge 2: An invincible zombie 问题的另一种解决方法

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该挑战的目的是僵尸碰到敌人时,将其设置为无敌模式,具体要求如下:

? You should create a variable property to track whether or not the zombie is invincible.
? If the zombie is invincible, you shouldn’t bother enumerating the scene’s cat ladies.
? If the zombie collides with a cat lady, don’t remove the cat lady from the scene. Instead, set the zombie as invincible. Next, run a sequence of actions that first makes the zombie blink 10 times over three seconds, then runs the block of code described below.
? Theblockofcodeshouldsethiddentofalseonthezombie,makingsurehe’s visible at the end no matter what, and set the zombie as no longer invincible.

书上的实现如下:

func zombieHitEnemy(enemy: SKSpriteNode) {
    enemy.removeFromParent()
    runAction(enemyCollisionSound)

    invincible = true
    let blinkTimes = 10.0
    let duration = 3.0
    let blinkAction = SKAction.customActionWithDuration(duration) { node, elapsedTime in
      let slice = duration / blinkTimes
      let remainder = Double(elapsedTime) % slice
      node.hidden = remainder > slice / 2
    }
    let setHidden = SKAction.runBlock() {
      self.zombie.hidden = false
      self.invincible = false
    }
    zombie.runAction(SKAction.sequence([blinkAction, setHidden]))

  }

func checkCollisions(){
        if invincible {
      return
    }

    var hitEnemies: [SKSpriteNode] = []
    enumerateChildNodesWithName("enemy") { node, _ in
      let enemy = node as! SKSpriteNode
      if CGRectIntersectsRect(
        CGRectInset(node.frame, 20, 20), self.zombie.frame) {
        hitEnemies.append(enemy)
      }
    }
    for enemy in hitEnemies {
      zombieHitEnemy(enemy)
    }
}

我觉得有几点可以完善的地方:

1. 每次都需要新建blinkAction,有点浪费.可以使用共享Action
2. 僵尸变为无敌后,如果敌人出现够快还是会删除其他敌人

我把blinkAction设置为lazy的计算属性,然后直接在场景子节点枚举中处理与敌人的碰撞,然后直接跳出遍历,这可以保证只会删除第一个碰撞的敌人:

lazy var blinkAction:SKAction = {
        let blinkTimes = 10.0
        let duration = 3.0
        let blinkAction = SKAction.customActionWithDuration(duration){node,elapsedTime in
            let slice = duration/blinkTimes
            let remainder = Double(elapsedTime) % slice
            node.hidden = remainder > slice / 2
        }
        return blinkAction
    }()

func checkCollisions(){
        if zombieInvincible{
            return
        }

        var hitEnemies:[SKSpriteNode] = []
        enumerateChildNodesWithName("enemy"){node,stop in
            let enemy = node as! SKSpriteNode
            if CGRectIntersectsRect(CGRectInset(enemy.frame, 20, 20), self.zombie.frame){
                hitEnemies.append(enemy)
                self.zombieInvincible = true
                let seq = SKAction.sequence([self.blinkAction,SKAction.runBlock(){
                        self.zombie.hidden = false
                        self.zombieInvincible = false
                    }])
                self.zombie.runAction(seq)
                stop.memory = true
            }
        }
        for enemy in hitEnemies{
            zombieHitEnemy(enemy)
        }
    }