1： NSTimer不能置零導(dǎo)致VC不釋放。導(dǎo)致內(nèi)存泄露

1.1 解決的實(shí)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()
  }
}

結(jié)果能不能釋放控制器那, 有沒有問題

• 1: 單純是pop沒有問題, 沒有深層的push. 沒有問題
• 2: 如果有深層的跳轉(zhuǎn), 比如當(dāng)前的控制器的定時(shí)器是控制倒計(jì)時(shí), 圖片輪播的盐茎， 這樣我們的push的時(shí)候 定時(shí)就停掉了兴垦，所以這個(gè)方法不可取

1.2 解決的實(shí)例方法二:

和方法一類似 但是在離開當(dāng)前的視圖的時(shí)候 做一個(gè)判斷, 判斷是pop還是push

具體步驟：
1: 視圖展示的時(shí)候記錄一下, 當(dāng)前導(dǎo)航控制器的子控制器的數(shù)量
2: 視圖離開(包括pop.push), 當(dāng)前導(dǎo)航控制器的childVc的數(shù)量, 與之前的做一個(gè)比較

注: push.pop 是 壓棧和出棧的過程, 修改navVc的子控制器的數(shù)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
    }
    // 如果當(dāng)前的控制器數(shù)量大于一開始的數(shù)量 說明是push
    // 如果小于 說明是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")
  }
}