ViewController对象为nil [英] ViewController object is nil

问题描述

我有2个视图控制器.
1. ViewController(VC)
2. WebViewController(WVC)

I have 2 view controller.
1. ViewController (VC)
2. WebViewController (WVC)

在VC中，我单击一个按钮，然后显示WVC.在WVC中成功完成所有任务之后，我想展示VC并在VC中执行特定功能.

In VC I click on a button and WVC is shown. After successfully completing all tasks in WVC, I want to show VC and execute a particular function in VC.

现在，情节提要包含一些对象，并通过单击和拖动将其添加到VC.最初，它具有一些值(不是nil).我单击按钮，按下WVC，完成WVC中的所有任务后，推送了VC.

Now, Storyboard contains some objects and add to VC using click and drag. Initially, it has some values(not nil). I Click on button, WVC is pushed, After completing all task in WVC, VC is pushed.

现在VC中的某些值为nil.错误，欢迎( UILabel ， UIView )为零...而且也是想在VC中调用函数.怎么可能.?

Now some values in VC is nil. error,welcome (UILabel, UIView) is nil... And also is want to call a function in VC. How it is possible.?

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
       }
   })
 }
}

推荐答案

您将VC推向WVC的方法很简单，因此，在将WVC推送到NavigationController之后，从逻辑上讲.它将WVC添加到了Navigation Stack的顶部.&最好从导航"中弹出此WVC，它将自动显示具有先前值的VC.

Simple your are pushing VC to WVC, So logically after pushing WVC to NavigationController. it added WVC to the top of Navigation Stack. & it it better to pop this WVC from Navigation will automatically show VC with previous values.

使用此

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)
       }
      })
  }
}

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