swift - 如果达到一定分数则添加 Sprite

Question

我有一个简单的游戏。您从一个球开始，然后弹跳直到获得 10 分。当你达到 10 分时，另一个球会出现(这样可以更快地到达下一个地标)。当达到 20 分时，出现第三个球。我已经设置好了，但我需要知道如何使用 case 执行 if 语句。

这是我要实现的语句。

   if (score == 10) && secondball.parent == nil {

这是我目前所拥有的:

import SpriteKit

class GameScene: SKScene {

override func didMoveToView(view: SKView) {

let ball = Ball()

    ball.position = CGPoint(x:self.frame.midX, y:440)

    addChild(ball)



    ball.physicsBody = SKPhysicsBody(circleOfRadius: 90)
    ball.physicsBody?.dynamic = true
    ball.physicsBody?.allowsRotation = false

    ball.physicsBody?.friction = 0
    ball.physicsBody?.angularDamping = 0
    ball.physicsBody?.linearDamping = 0
    ball.physicsBody?.usesPreciseCollisionDetection = true
    ball.physicsBody!.categoryBitMask = 0




override func update(currentTime: CFTimeInterval) {


    if shouldUpdateTexture {
        shouldUpdateTexture = false
        switch score {
    case 10...19: backgroundNode.texture = SKTexture(imageNamed: "orangebackground")

            let secondball = Ball()
            secondball.position = CGPoint(x:self.frame.midX * 1.65, y: 440)
            addChild(secondball)



            secondball.physicsBody = SKPhysicsBody(circleOfRadius: 90)
            secondball.physicsBody?.dynamic = true
            secondball.physicsBody?.allowsRotation = false

            secondball.physicsBody?.friction = 0
            secondball.physicsBody?.angularDamping = 0
            secondball.physicsBody?.linearDamping = 0
            secondball.physicsBody?.usesPreciseCollisionDetection = true
            secondball.physicsBody!.categoryBitMask = 0



    case 20...29: backgroundNode.texture = SKTexture(imageNamed: "yellowbackground")

    let thirdball = Ball()
    thirdball.position = CGPoint(x:self.frame.midX * 0.35, y:440)
    addChild(thirdball)



    thirdball.physicsBody = SKPhysicsBody(circleOfRadius: 90)
    thirdball.physicsBody?.dynamic = true
    thirdball.physicsBody?.allowsRotation = false

    thirdball.physicsBody?.friction = 0
    thirdball.physicsBody?.angularDamping = 0
    thirdball.physicsBody?.linearDamping = 0
    thirdball.physicsBody?.usesPreciseCollisionDetection = true
    thirdball.physicsBody!.categoryBitMask = 0

    case 30...39: backgroundNode.texture = SKTexture(imageNamed: "greenbackground")
    case 40...49: backgroundNode.texture = SKTexture(imageNamed: "bluebackground")
    case 50...59: backgroundNode.texture = SKTexture(imageNamed: "darkbluebackground")

    if ball.parent != nil {
        let ball = Ball()

        ball.position = CGPoint(x:self.frame.midX, y:440)

        addChild(ball)



        ball.physicsBody = SKPhysicsBody(circleOfRadius: 90)
        ball.physicsBody?.dynamic = true
        ball.physicsBody?.allowsRotation = false

        ball.physicsBody?.friction = 0
        ball.physicsBody?.angularDamping = 0
        ball.physicsBody?.linearDamping = 0
        ball.physicsBody?.usesPreciseCollisionDetection = true
        ball.physicsBody!.categoryBitMask = 0


            }

case:10...19 有效，case:20...29 也有效，但对于 case 50...59 如果前一个球不存在，我只希望另一个球出现。

如果您需要更多或更少的信息，请在下方评论。我会立即更新。

------更新----代码运行良好，除非分数达到 50 以检查球是否存在。

谢谢，乔丹。

Answer 1

在 case 50...59: 中，只需添加一个 if 语句来检查球是否已经存在。添加这样的内容:

if thirdBall.parent == nil {

addChild(thirdBall)
// Whatever other code you want to run only if the ball needs to be added to the scene

}

希望这对您有所帮助!