Swift游戏实战-跑酷熊猫 09 移除场景之外的平台

if platforms[0].position.x < -platforms[0].width {
        platforms[0].removeFromParent()
        platforms.removeAtIndex(0)
}

import SPriteKit

class PlatformFactory:SKNode{
    let textureLeft = SKTexture(imageNamed: "platform_l")
    let textureMid = SKTexture(imageNamed: "platform_m")
    let textureRight = SKTexture(imageNamed: "platform_r")

    var platforms = [Platform]()
    var sceneWidth : CGFloat = 0
    var delegate:ProtocolMainScene?

    func createPlatformRandom(){
        let midNum:UInt32 = arc4random()%4 + 1
        let gap:CGFloat = CGFloat(arc4random()%8 + 1)
        let x:CGFloat = self.sceneWidth + CGFloat(midNum*50) + gap + 100
        let y:CGFloat = CGFloat(arc4random()%200+200)
        createPlatform(midNum, x: x, y: y)
    }

    func createPlatform(midNum:UInt32,x:CGFloat,y:CGFloat){
        let platform = Platform()
        platform.position = CGPointMake(x, y)

        let platform_left = SKSpriteNode(texture: textureLeft)
        platform_left.anchorPoint = CGPointMake(0, 0.9)
       

        let platform_right = SKSpriteNode(texture: textureRight)
        platform_right.anchorPoint = CGPointMake(0, 0.9)
       

        var arrPlatform = [SKSpriteNode]()

        arrPlatform.append(platform_left)
       
       
        for i in 1...midNum {
            let platform_mid = SKSpriteNode(texture: textureMid)
            platform_mid.anchorPoint = CGPointMake(0, 0.9)
            arrPlatform.append(platform_mid)
        }

        arrPlatform.append(platform_right)
       
        platform.onCreate(arrPlatform)
       
        self.addChild(platform)
       
        platforms.append(platform)
        //通用公式：生成的平台的长度 + 平台的x坐标 - 主场景的宽度
        delegate?.onGetData(platform.width + x - sceneWidth)
       
    }

    func move(speed:CGFloat){
        for p in platforms {
            p.position.x -= speed
        }
        if platforms[0].position.x < -platforms[0].width {
            platforms[0].removeFromParent()
            platforms.removeAtIndex(0)
        }
    }
}