NotificationCenter Selector方法未在Swift中调用

Question

I am trying to send first viewcontroller textfield data into second viewcontroller label.

In first controller, Inside send action button adding notification post method

 @IBAction func sendtBtn(_ sender: Any) {
    let secVc = storyboard?.instantiateViewController(withIdentifier: "SecondViewController") as! SecondViewController
    self.navigationController?.pushViewController(secVc, animated: true)

     NotificationCenter.default.post(name: Notification.Name( "notificationName"), object: nil, userInfo: ["text": firstTextField.text])
   }

And second viewcontroller addobserver method inside view didload

   NotificationCenter.default.addObserver(self, selector: #selector(self.showMsg(_:)), name: Notification.Name( "notificationName"), object: nil)

Selector function :

func showMsg(_ notification: Notification){
    print("helloooo")
    var vcData = notification.userInfo?["text"]
    firstLabel.text = vcData as! String
}

When keeping break points for add observer it observers but it does not calling showMsg function. Please help me in this code.

Answer 1

You do have the reference to the second view controller. There is no reason at all to use Notification . Don't use notifications if there is only one receiver and the objects are related.

The code doesn't work because the view is not loaded yet when the notification is sent.

Forget the notification. Instead create a property in the second view controller, assign the value in sendtBtn and show the message in viewDidLoad

@IBAction func sendtBtn(_ sender: Any) {
    let secVc = storyboard?.instantiateViewController(withIdentifier: "SecondViewController") as! SecondViewController
    secVc.message = firstTextField.text
    self.navigationController?.pushViewController(secVc, animated: true)

}

Second view controller

var message = ""

func viewDidLoad() {
    super.viewDidLoad()
    firstLabel.text = message
}