问使用Swift中的SKSpriteNode和SKAction创建具有随机Y坐标的视差云

EN

func addClouds() {

        let cloud1 = SKSpriteNode(imageNamed: "cloud1")
        let cloud2 = SKSpriteNode(imageNamed: "cloud2")
        let cloud3 = SKSpriteNode(imageNamed: "cloud3")
        let cloud4 = SKSpriteNode(imageNamed: "cloud4")
        let cloud5 = SKSpriteNode(imageNamed: "cloud5")

        cloud1.zPosition = ZIndexPosition.CLOUD
        cloud1.position = CGPoint(x: self.FRAME_WIDTH - 100, y: self.FRAME_HEIGHT / 2 - 150)
        cloud1.size = CGSize(width: 44, height: 14)

        cloud2.zPosition = ZIndexPosition.CLOUD
        cloud2.position = CGPoint(x: self.FRAME_WIDTH + 150, y: self.FRAME_HEIGHT - 100)
        cloud2.size = CGSize(width: 104, height: 16)

        cloud3.zPosition = ZIndexPosition.CLOUD
        cloud3.position = CGPoint(x: self.FRAME_WIDTH - 50, y: self.FRAME_HEIGHT - 200)
        cloud3.size = CGSize(width: 8, height: 6)

        cloud4.zPosition = ZIndexPosition.CLOUD
        cloud4.position = CGPoint(x: self.FRAME_WIDTH + 200, y: self.FRAME_HEIGHT / 2 - 50)
        cloud4.size = CGSize(width: 116, height: 32)

        cloud5.zPosition = ZIndexPosition.CLOUD
        cloud5.position = CGPoint(x: self.FRAME_WIDTH, y: self.FRAME_HEIGHT - 250)
        cloud5.size = CGSize(width: 24, height: 6)


        let resetCloud1YPos = SKAction.moveToY(self.randomCloud1, duration: 0)
        let resetCloud2YPos = SKAction.moveToY(self.randomCloud2, duration: 0)
        let resetCloud3YPos = SKAction.moveToY(self.randomCloud3, duration: 0)
        let resetCloud4YPos = SKAction.moveToY(self.randomCloud4, duration: 0)
        let resetCloud5YPos = SKAction.moveToY(self.randomCloud5, duration: 0)

        let resetCloud1Pos = SKAction.moveToX((self.FRAME_WIDTH * 2) - 100, duration: 0)
        let resetCloud2Pos = SKAction.moveToX((self.FRAME_WIDTH * 2) - 150, duration: 0)
        let resetCloud3Pos = SKAction.moveToX((self.FRAME_WIDTH * 2) - 50, duration: 0)
        let resetCloud4Pos = SKAction.moveToX((self.FRAME_WIDTH * 2) - 200, duration: 0)
        let resetCloud5Pos = SKAction.moveToX((self.FRAME_WIDTH * 2) - 20, duration: 0)

        let moveCloud1 = SKAction.moveToX(-100, duration: 28)
        let cloud1Sequence = SKAction.sequence([moveCloud1, resetCloud1Pos, resetCloud1YPos])
        let cloud1Forever = SKAction.repeatActionForever(cloud1Sequence)

        let moveCloud2 = SKAction.moveToX(-100, duration: 24)
        let cloud2Sequence = SKAction.sequence([moveCloud2, resetCloud2Pos, resetCloud2YPos])
        let cloud2Forever = SKAction.repeatActionForever(cloud2Sequence)

        let moveCloud3 = SKAction.moveToX(-100, duration: 35)
        let cloud3Sequence = SKAction.sequence([moveCloud3, resetCloud3Pos, resetCloud3YPos])
        let cloud3Forever = SKAction.repeatActionForever(cloud3Sequence)

        let moveCloud4 = SKAction.moveToX(-100, duration: 13)
        let cloud4Sequence = SKAction.sequence([moveCloud4, resetCloud4Pos, resetCloud4YPos])
        let cloud4Forever = SKAction.repeatActionForever(cloud4Sequence)

        let moveCloud5 = SKAction.moveToX(-100, duration: 18)
        let cloud5Sequence = SKAction.sequence([moveCloud5, resetCloud5Pos, resetCloud5YPos])
        let cloud5Forever = SKAction.repeatActionForever(cloud5Sequence)

        cloud1.runAction(cloud1Forever)
        cloud2.runAction(cloud2Forever)
        cloud3.runAction(cloud3Forever)
        cloud4.runAction(cloud4Forever)
        cloud5.runAction(cloud5Forever)

        self.addChild(cloud1)
        self.addChild(cloud2)
        self.addChild(cloud3)
        self.addChild(cloud4)
        self.addChild(cloud5)

    }