ios - 如何使用 arc4random 从数组中选择随机 SKShapeNode？

Question

我正在尝试使用 sprite kit 和 swift 制作我的第一个应用程序。我创建了一个数组并用两个形状节点填充它(如下所示。

    //name the properties for enemy 1
    enemy1 = SKShapeNode (rectOfSize: CGSize(width: rectWidth/10, height: rectHeight/10))
    enemy1.position = first
    enemy1.fillColor = UIColor.blackColor()
    enemy1.physicsBody = SKPhysicsBody(rectangleOfSize: CGSize(width: rectWidth, height: rectHeight))
    enemy1.physicsBody?.dynamic = true
    enemy1.physicsBody?.affectedByGravity = false

    //name the properties for enemy 2
    enemy2 = SKShapeNode (rectOfSize: CGSize(width: rectWidth/10, height: rectHeight/10))
    enemy2.position = second
    enemy2.fillColor = UIColor.blackColor()
    enemy2.physicsBody = SKPhysicsBody(rectangleOfSize: CGSize(width: rectWidth, height: rectHeight))
    enemy2.physicsBody?.dynamic = true
    enemy2.physicsBody?.affectedByGravity = false



    //populate the arrays
    arrayOfEnemies1.addObject(enemy1)
    arrayOfEnemies1.addObject(enemy2)

假设我想每 2 秒将这些节点之一随机添加到场景中。我知道使用 arc4random，但我不确定该怎么做。任何帮助将不胜感激。谢谢!

Answer 1

您可以创建一个扩展并获得这样的随机数组元素:

extension Array {
    func randomElement() -> T {
        let index = Int(arc4random_uniform(UInt32(self.count)))
        return self[index]
    }
}

像那样:

var randomElement = arrayOfEnemies1.randomElement()