如何在UIAlertController中添加倒计时定时器

// 创建UIAlertController对象
let alertController = UIAlertController(title: "倒计时", message: "剩余时间：", preferredStyle: .alert)

// 创建UILabel对象
let countdownLabel = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 30))
countdownLabel.textAlignment = .center
countdownLabel.font = UIFont.systemFont(ofSize: 20)
countdownLabel.text = "10" // 初始倒计时值
alertController.view.addSubview(countdownLabel)

// 创建定时器
var countdown = 10
let timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { timer in
    countdown -= 1
    countdownLabel.text = "\(countdown)"
    
    if countdown == 0 {
        timer.invalidate()
        alertController.dismiss(animated: true, completion: nil)
    }
}

// 将定时器添加到当前RunLoop中
RunLoop.current.add(timer, forMode: .common)

// 显示UIAlertController
present(alertController, animated: true, completion: nil)