class MyViewController: BaseViewController {
    var dispalyingCellArray = [UITableViewCell]()
    var timer: Timer?

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        let nib0 = UINib(nibName: "MyCell0", bundle: nil)
        tableView.register(nib0, forCellReuseIdentifier: "MyCell0ID")
        tableView.rowHeight = UITableViewAutomaticDimension
        tableView.estimatedRowHeight = 360.0
      }
      override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        //启动定时器
        setupTimer()
      }
        override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        //关闭定时器
        destroyTimer()
    }
    
    func destroyTimer() {
        if timer != nil {
            if timer!.isValid {
                timer?.invalidate()
            }
            timer = nil
        }
    }
    
    func setupTimer() {
        destroyTimer()
        timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(timerRepeats), userInfo: nil, repeats: true)
    }
    
        @objc func timerRepeats() {
        for encell in dispalyingCellArray {//遍历当前显示的cell数组，每个cell都进行刷新
            if let cell0 = encell as? MyCell0 {
                cell0.refreshTime()
            }
        }
    }
 }

extension MyViewController: UITableViewDataSource, UITableViewDelegate {
  ...    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "MyCell0ID") as! MyCell0
        return cell
      }
    
//通过下面两步，可以维持一个仅包含当前显示的cell的数组，timer中遍历该数组，刷新所有的（当前显示的）cell！
    func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
        dispalyingCellArray.append(cell)    //保存当前显示的cell到数组
    }
    
    func tableView(_ tableView: UITableView, didEndDisplaying cell: UITableViewCell, forRowAt indexPath: IndexPath) {
        if let index = dispalyingCellArray.index(of: cell) {
            dispalyingCellArray.remove(at: index)//把被滚出屏幕的cell移除
        }
    }
  
}