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。

Swift 5+(带警报控制的后退按钮)

override func viewDidLoad() {
        super.viewDidLoad()
        
        self.navigationItem.hidesBackButton = true
        let newBackButton = UIBarButtonItem(title: "<Back", style: UIBarButtonItem.Style.plain, target: self, action: #selector(PGWebViewController.back(sender:)))
        self.navigationItem.leftBarButtonItem = newBackButton
}


@objc func back(sender: UIBarButtonItem) {
    
    let alert = UIAlertController(title: "Warning!", message: "Your payment process is not completed yet. Do you want to go back?", preferredStyle: .alert)
        
         let ok = UIAlertAction(title: "OK", style: .default, handler: { action in
             _ = self.navigationController?.popViewController(animated: true)
         })
         alert.addAction(ok)
         let cancel = UIAlertAction(title: "Cancel", style: .default, handler: { action in
         })
         alert.addAction(cancel)
         DispatchQueue.main.async(execute: {
            self.present(alert, animated: true)
    })}

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)
    }
}

试试这个。

self.navigationItem.leftBarButtonItem?.target = "methodname"
func methodname ( ) {            
  //    enter code here
}

这个也试试。

override func viewWillAppear(animated: Bool) {
  //empty your array
}

你可以简单地从堆栈中删除不必要的控制器，就像这样:

self.navigationController?.viewControllers.removeAll(where: {
        $0 is FirstViewController || $0 is SecondWithPinController
    })

如果你想有后退按钮和后退箭头，你可以使用下面的图片和代码

backArrow.png backArrow@2x.png backArrow@3x.png

override func viewDidLoad() {
    super.viewDidLoad()
    let customBackButton = UIBarButtonItem(image: UIImage(named: "backArrow") , style: .plain, target: self, action: #selector(backAction(sender:)))
    customBackButton.imageInsets = UIEdgeInsets(top: 2, left: -8, bottom: 0, right: 0)
    navigationItem.leftBarButtonItem = customBackButton
}

func backAction(sender: UIBarButtonItem) {
    // custom actions here
    navigationController?.popViewController(animated: true)
}