Swift transit from vc to another vc-CodePudding

ViewController has a label and a button for go to secondVC. And secondVC has a text field , label , button to write user-entered text in the text field on the label. When user press the back button of navigation bar, I want transit secondVC's label's text to ViewController's label's text. How can I do this ?

ViewController's code:

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var nameLabel: UILabel!
    override func viewDidLoad() {
        super.viewDidLoad()
    }

    @IBAction func goVC2(_ sender: Any) {
        performSegue(withIdentifier: "toVC2", sender: nil)
    }
  
    
}

secondVC's code:

import UIKit

class secondVC: UIViewController {

    @IBOutlet weak var nameField: UITextField!
    @IBOutlet weak var resultLabel: UILabel!
   
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    

    @IBAction func saveClicked(_ sender: Any) {
        resultLabel.text = nameField.text
    }
    
}

I tried prepare for segue in ViewController and but it was error. And I searched on google for this but I couldn't find solution.

CodePudding user response：

Use protocol for pass data from second VC to first VC. you need to create your own delegate method and call on dismiss with pass data, check below code :----

ViewController's code:

import UIKit

class ViewController: UIViewController, Delegate {

    @IBOutlet weak var nameLabel: UILabel!
    override func viewDidLoad() {
        super.viewDidLoad()
    }

    func save(str : String) {
        self.nameLabel.text = str
    }

    @IBAction func goVC2(_ sender: Any) {
       if let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "secondVC") as? secondVC {
                               
           vc.delegate = self
           self.present(vc, animated: true, completion: nil)
         }
    }
  
    
}

secondVC's code:

import UIKit

protocol Delegate : AnyObject {
    func save(str : String)
}

class secondVC: UIViewController {

    @IBOutlet weak var nameField: UITextField!
    @IBOutlet weak var resultLabel: UILabel!
    weak var delegate : Delegate?
   
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    

    @IBAction func saveClicked(_ sender: Any) {

       if let del = self.delegate {
                
            let txt = nameField.text
            del.save(str: txt)
            self.dismiss(animated: true, completion: nil)
        }
        
    }
    
}