1： NSTimer不能置零导致VC不释放。导致内存泄露

1.1 解决的实例方法一:

import UIKit

class TwoViewController: UIViewController {

  var customTimer:Timer?
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor.orange
      customTimer = Timer.init(timeInterval: 1, target: self, selector: #selector(TwoViewController.timrClick(sender:)), userInfo: self, repeats: true)
      RunLoop.current.add(customTimer!, forMode: RunLoopMode.commonModes)
    }

  func timrClick(sender:Timer)  {
    print("timrClick: \(sender.timeInterval)")
  }


  deinit {
    print("\(object_getClass(self)) delloc")
  }

  override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    customTimer?.invalidate()
  }
}

结果能不能释放控制器那, 有没有问题

• 1: 单纯是pop没有问题, 没有深层的push. 没有问题
• 2: 如果有深层的跳转, 比如当前的控制器的定时器是控制倒计时, 图片轮播的， 这样我们的push的时候 定时就停掉了，所以这个方法不可取

1.2 解决的实例方法二:

和方法一类似 但是在离开当前的视图的时候 做一个判断, 判断是pop还是push

具体步骤：
1: 视图展示的时候记录一下, 当前导航控制器的子控制器的数量
2: 视图离开(包括pop.push), 当前导航控制器的childVc的数量, 与之前的做一个比较

注: push.pop 是 压栈和出栈的过程, 修改navVc的子控制器的数量  

import UIKit

class TwoViewController: UIViewController {

  var vcCount = 0
  var customTimer:Timer?


  override func viewDidLoad() {
    super.viewDidLoad()
    view.backgroundColor = UIColor.orange

    vcCount = (self.navigationController?.viewControllers.count)!

    customTimer = Timer.init(timeInterval: 1, target: self, selector: #selector(TwoViewController.timrClick(sender:)), userInfo: self, repeats: true)
    RunLoop.current.add(customTimer!, forMode: RunLoopMode.commonModes)
  }


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

    guard let tmpCount = self.navigationController?.viewControllers.count else {
      return
    }
    // 如果当前的控制器数量大于一开始的数量 说明是push
    // 如果小于 说明是pop
    if tmpCount < vcCount {
      self.customTimer?.invalidate()
      self.customTimer = nil
    }
  }


  func timrClick(sender:Timer)  {
    print("timrClick: \(sender.timeInterval)")
  }


  override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    self.navigationController?.pushViewController(ThreeViewController(), animated: true)
  }

  deinit {
    print("\(object_getClass(self)) delloc")
  }
}