如何在不按停止按钮的情况下退出视图控制器时关闭Countdowntimer？

import UIKit

class ViewController: UIViewController {
    var countdownTimer: Timer?
    var remainingTime = 60 // 设置倒计时时间为60秒

    override func viewDidLoad() {
        super.viewDidLoad()
        startCountdownTimer()
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        stopCountdownTimer()
    }

    func startCountdownTimer() {
        countdownTimer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(updateCountdown), userInfo: nil, repeats: true)
    }

    @objc func updateCountdown() {
        if remainingTime > 0 {
            remainingTime -= 1
            // 更新UI显示剩余时间
        } else {
            stopCountdownTimer()
        }
    }

    func stopCountdownTimer() {
        countdownTimer?.invalidate()
        countdownTimer = nil
    }
}