Swift 延迟问题

Question

所以我一直致力于创建一个应用程序，如果您按下按钮，它就会触发startGame。然后，这应该等待我在更改每个图像之前创建的延迟。延迟是有效的，但它们是在我启动应用程序时立即开始的，而不是在我按下按钮时开始的。从那以后我一直在努力修复它。有什么建议吗？

感谢您的帮助!

这是我认为更重要的代码:

let deadlineTime = DispatchTime.now() + .seconds(1)
let deadlineTime2 = DispatchTime.now() + .seconds(2)
let deadlineTime3 = DispatchTime.now() + .seconds(3)
let deadlineTime4 = DispatchTime.now() + .seconds(4)

@IBAction func startGame(_ sender: AnyObject) {

        trumpImage.isHidden = false

        DispatchQueue.main.asyncAfter(deadline: deadlineTime) {

            self.trumpImage.image = UIImage(named: "trumpTurnOne")

        }

        DispatchQueue.main.asyncAfter(deadline: deadlineTime2) {

            self.trumpImage.image = UIImage(named: "trumpTurnTwo")

        }

        DispatchQueue.main.asyncAfter(deadline: deadlineTime3) {

            self.trumpImage.image = UIImage(named: "trumpTurnThree")

        }

        DispatchQueue.main.asyncAfter(deadline: deadlineTime4) {

                self.runGame()

        }

}

Answer 1

试试这个:

let deadlineTime = {return DispatchTime.now() + .seconds(1)}
let deadlineTime2 = {return DispatchTime.now() + .seconds(2)}
let deadlineTime3 = {return DispatchTime.now() + .seconds(3)}
let deadlineTime4 = {return DispatchTime.now() + .seconds(4)}

如果您已将四个 DispatchTime 声明为实例属性，则初始值的计算将在实例生成时进行，而不是在实际使用这些属性时进行。这意味着 DispatchTime.now() 代表实例化的时间，它可能远远早于用户按下按钮的时间。

因此，要使 DispatchTime.now() 表示按下按钮的时间，您可能需要将它们设置为计算属性。否则，您需要将它们设为局部变量。

@IBAction func startGame(_ sender: AnyObject) {
    let deadlineTime = DispatchTime.now() + .seconds(1)
    let deadlineTime2 = DispatchTime.now() + .seconds(2)
    let deadlineTime3 = DispatchTime.now() + .seconds(3)
    let deadlineTime4 = DispatchTime.now() + .seconds(4)

    //...
}