如何修复此代码以允许计时器在用户单击UIAlert时开始计时？

var timer: Timer?
var isTimerRunning = false

let alertController = UIAlertController(title: "开始计时器", message: "单击确定开始计时器", preferredStyle: .alert)
let startAction = UIAlertAction(title: "确定", style: .default) { (_) in
    self.startTimer()
}
alertController.addAction(startAction)
present(alertController, animated: true, completion: nil)

func startTimer() {
    if !isTimerRunning {
        timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(updateTimer), userInfo: nil, repeats: true)
        isTimerRunning = true
    }
}

@objc func updateTimer() {
    // 更新计时器的显示
    print("计时器正在运行...")
}