如果你正在使用navigationController，那么将UINavigationControllerDelegate协议添加到类中，并添加delegate方法，如下所示:

class ViewController:UINavigationControllerDelegate {

    func navigationController(navigationController: UINavigationController, willShowViewController viewController: UIViewController,
animated: Bool) {
        if viewController === self {
            // do here what you want
        }
    }
}

每当导航控制器滑到新屏幕时，就调用此方法。如果返回按钮被按下，新的视图控制器就是ViewController本身。

我通过调用/重写viewWillDisappear来实现这一点，然后像这样访问navigationController的堆栈:

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

    let stack = self.navigationController?.viewControllers.count

    if stack >= 2 {
        // for whatever reason, the last item on the stack is the TaskBuilderViewController (not self), so we only use -1 to access it
        if let lastitem = self.navigationController?.viewControllers[stack! - 1] as? theViewControllerYoureTryingToAccess {
            // hand over the data via public property or call a public method of theViewControllerYoureTryingToAccess, like
            lastitem.emptyArray()
            lastitem.value = 5
        }
    }
}

对于Swift 5，我们可以检查它在视图中是否会消失

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

    if self.isMovingFromParent {
        delegate?.passValue(clickedImage: selectedImage)
    }
}

只需control +拖动栏项到func下面。魅力工作

@IBAction func done(sender: AnyObject) {
    if((self.presentingViewController) != nil){
        self.dismiss(animated: false, completion: nil)
        print("done")
    }
}

    override public func viewDidLoad() {
         super.viewDidLoad()
         self.navigationController?.navigationBar.topItem?.title = GlobalVariables.selectedMainIconName
         let image = UIImage(named: "back-btn")

         image = image?.imageWithRenderingMode(UIImageRenderingMode.AlwaysOriginal)

        self.navigationItem.leftBarButtonItem = UIBarButtonItem(image: image, style: UIBarButtonItemStyle.Plain, target: self, action: #selector(Current[enter image description here][1]ViewController.back) )
    }

    func back() {
      self.navigationController?.popToViewController( self.navigationController!.viewControllers[ self.navigationController!.viewControllers.count - 2 ], animated: true)
    }

你可以子类化UINavigationController并重写popViewController(animated: Bool)。除了能够在那里执行一些代码，你还可以防止用户完全返回，例如提示保存或丢弃他当前的工作。

示例实现，其中您可以设置popHandler，由推送的控制器设置/清除。

class NavigationController: UINavigationController
{
    var popHandler: (() -> Bool)?

    override func popViewController(animated: Bool) -> UIViewController?
    {
        guard self.popHandler?() != false else
        {
            return nil
        }
        self.popHandler = nil
        return super.popViewController(animated: animated)
    }
}

以及来自跟踪未保存工作的推送控制器的示例使用情况。

let hasUnsavedWork: Bool = // ...
(self.navigationController as! NavigationController).popHandler = hasUnsavedWork ?
    {
        // Prompt saving work here with an alert

        return false // Prevent pop until as user choses to save or discard

    } : nil // No unsaved work, we clear popHandler to let it pop normally

作为一个很好的触摸，这也将被interactivePopGestureRecognizer调用，当用户试图返回使用滑动手势。