为什么关闭视图控制器不会从内存中清除呈现的控制器？

Question

我有2个控制器。他们每个人在屏幕上只有一个按钮。对于第一个控制器按钮是模态呈现第二个控制器，对于第二个控制器按钮是解散呈现的控制器。

第一个密码简单如门：

class ViewController: UIViewController {
    @IBAction func present(sender: AnyObject) {
        let storyboard = UIStoryboard(name: "Main", bundle: NSBundle.mainBundle())
        if let controller = storyboard.instantiateViewControllerWithIdentifier("web") as? UIViewController {
            controller.modalTransitionStyle = UIModalTransitionStyle.FlipHorizontal
            self.presentViewController(controller, animated: true, completion: nil)
        }
    }
}

第二个控制器代码包含一些额外的代码，用于检测在关闭控制器后仍然存在。

static var index: Int = 0
var index: Int

required init(coder aDecoder: NSCoder) {
    self.index = WebViewController.index++
    super.init(coder: aDecoder)
    let timer = NSTimer.scheduledTimerWithTimeInterval(5, target: self, selector: "action", userInfo: nil, repeats: true)
}

func action() {
    NSLog("Class \(self.dynamicType) index is \(self.index)")
}

第二个控制器的所有代码如下：

class WebViewController: UIViewController {
    static var index: Int = 0
    var index: Int

    required init(coder aDecoder: NSCoder) {
        self.index = WebViewController.index++
        super.init(coder: aDecoder)
        let timer = NSTimer.scheduledTimerWithTimeInterval(5, target: self, selector: "action", userInfo: nil, repeats: true)
    }

    func action() {
        NSLog("Class \(self.view) index is \(self.index)")
    }

    @IBAction func dismissSelf() {
        if let presentingController = self.presentingViewController {
            presentingController.dismissViewControllerAnimated(true, completion: nil)
        }
    }
}

因此，当您第一次运行在第一个控制器屏幕上按下按钮时，您将每隔 5 秒在控制台中看到如下内容：

Class Proj.WebViewController 索引为 0

但是如果您关闭控制器并再次出现，那么您将同时看到：

Class Proj.WebViewController 索引为 0

Class Proj.WebViewController 索引为 1

据我所知，解散并不是从内存中删除呈现的控制器，即使没有人从我身边抓住他。

有人知道这是什么吗？我该如何解决？

您也可以下载sample project

Answer 1

计时器正在捕获您的视图控制器

你应该保留一个weak reference到计时器，并在dismissSelf[=中添加timer.invalidate() 13=]

https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSTimer_Class/index.html#//apple_ref/occ/instm/NSTimer/invalidate

Answer 2

在 swift 中，如果您的对象被利用，那么编译器会理解它会被使用，所以即使您 dismissViewControllerAnimated UIViewController。它不会是 dealloc。所以你需要在 dismissViewControllerAnimated 触发之前 invalidate() 计时器。这里 dealloc 被替换为 deinit。

@IBAction func dismissSelf() {
        timer.invalidate()
        self.dismissViewControllerAnimated(true, completion: nil)
    }

deinit {

        self.view.removeFromSuperview()
        println("call")
        // perform the deinitialization
    }

希望对您有所帮助。

Answer 3

swift-nstimer-tutorial-lets-create-a-counter-application &simple-stopwatch-app-in-swift

NSTimer_Class

使用这个...

@IBAction func dismissSelf() {
        if let presentingController = self.presentingViewController {
            timer.invalidate()// add this
            presentingController.dismissViewControllerAnimated(true, completion: nil)
        }
    }

Answer 4

我也遇到过这种情况 "Why dismissing view controller is not clearing presented controller from memory?"。所以就我而言，我有

FirstViewController: UIViewController {
var secondViewController: SecondViewController
 override func viewDidLoad() {
      super.viewDidLoad()
      //Important...Don't Do instantiation here....
      //Instantiate only when it's going to be used
      secondViewController = UIStoryboard.init(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "SecondViewController") as? SecondViewController
 }
 @IBAction fun buttonAction() {
     self.present(secondViewController, animated: true)
 }
}

The Above Code didn't called deinit on my SecondViewController

对我有用的修复：

FirstViewController: UIViewController {
var secondViewController: SecondViewController
 override func viewDidLoad() {
      super.viewDidLoad()
 }
 @IBAction fun buttonAction() {
     //Do the instantiation here 
     secondViewController = UIStoryboard.init(name: "Main", bundle: nil)
                            .instantiateViewController(withIdentifier: "SecondViewController") as? SecondViewController
     self.present(secondViewController, animated: true)
     //setting the view controller reference variable to nil
     self.secondViewController = nil
 }
}

SecondViewController 的引用保留在 SecondViewController 变量上，直到它被重新初始化或设置为 nil。

为什么关闭视图控制器不会从内存中清除呈现的控制器？

Why dismissing view controller is not clearing presented controller from memory?

cocoa-touch

uikit

ios

swift