ios - ViewController 对象为 nil

Question

我有 2 个 View Controller 。
1. View Controller (VC)
2. WebView Controller (WVC)

在 VC 中，我单击一个按钮并显示 WVC。在成功完成 WVC 中的所有任务后，我想显示 VC 并在 VC 中执行特定功能。

现在，Storyboard 包含一些对象并通过单击和拖动添加到 VC。最初，它有一些值(不是零)。我单击按钮，推送 WVC，完成 WVC 中的所有任务后，VC被推送。

现在VC中有些值是nil。错误，欢迎 (UILabel, UIView) 为零...而且也是想在VC中调用一个函数。怎么可能？

代码

ViewController.swift

class LoginController:UIViewController,UITextFieldDelegate{
    @IBOutlet weak var password: UITextField!
    @IBOutlet weak var username: UITextField!
    @IBOutlet weak var error: UILabel!
    @IBOutlet weak var welocome: UILabel!

    ......

    @IBAction func BtnClicked(sender: AnyObject) {
     let webViewCnt = self.storyboard!.instantiateViewControllerWithIdentifier("WebViewController") as UIViewController
        self.navigationController?.pushViewController(webViewCnt, animated: true)
    }
    func doSomeProcess(){

    }
}

WebViewController.swift

class WebViewController: UIViewController, UITextFieldDelegate,UIWebViewDelegate {
 override func viewDidLoad() {
    super.viewDidLoad()
    webView.delegate = self

    self.start()
}
 func start(){
      ---- do some process ----
      dispatch_async(dispatch_get_main_queue(), { () -> Void in
        let ViewCont = self.storyboard!.instantiateViewControllerWithIdentifier("LoginController") as UIViewController

        self.navigationController?.pushViewController(ViewCont, animated: true)
        ViewController().doSomeProcess() // call viewcontroller doSomeProcess() function
       }
   })
 }
}

Answer 1

很简单，您正在将 VC 推向 WVC，所以在将 WVC 推送到 NavigationController 之后合乎逻辑。它将 WVC 添加到导航堆栈的顶部。最好从导航中弹出此 WVC 将自动显示具有先前值的 VC。

使用这个

ViewController.swift

class LoginController:UIViewController,UITextFieldDelegate{
    @IBOutlet weak var password: UITextField!
    @IBOutlet weak var username: UITextField!
    @IBOutlet weak var error: UILabel!
    @IBOutlet weak var welocome: UILabel!
    var isBackFromWVC = false
    ......

    @IBAction func BtnClicked(sender: AnyObject) {
       let webViewCnt = self.storyboard!.instantiateViewControllerWithIdentifier("WebViewController") as UIViewController
        self.navigationController?.pushViewController(webViewCnt, animated: true)   
       isBackFromWVC = true
    }
    func doSomeProcess(){

    }
    func vieWillAppear(){
      if(isBackFromWVC){
        doSomeProcess()
      }
   }
}

WebViewController.swift

class WebViewController: UIViewController, UITextFieldDelegate,UIWebViewDelegate {
 override func viewDidLoad() {
    super.viewDidLoad()
    webView.delegate = self

    self.start()
 }
 func start(){
      ---- do some process ----
      dispatch_async(dispatch_get_main_queue(), { () -> Void in

         self.navigationController?.popViewController(animated:true)
       }
      })
  }
}