将数据从detailViewController向后传递到masterViewController

Question

I am trying to pass data back from the second viewController. I can do that without NavigationController. But now I need to use NavigationController. Then my code does work as before. The data wont pass. Here is the simple code: In first viewController

class ViewController: UIViewController, backfromSecond {

    @IBOutlet weak var text: UILabel!

    var string : String?

    override func viewDidLoad() {
        super.viewDidLoad()
        self.string = "Start here"
    }
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(true)
        self.text.text = self.string
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if let destinationViewController = segue.destination as? secondViewController{
            destinationViewController.delegate = self
        }
    }

    func back(text: String) {
        self.string = text
        print(text)
    }
}

And Second viewController:

    protocol backfromSecond {
    func back(text: String)
    } 
    class secondViewController: UIViewController {
    var string : String = "nothing here"
    var delegate : backfromSecond?
    override func viewDidLoad() {
        super.viewDidLoad()
        delegate?.back(text: string)
        // Do any additional setup after loading the view.
    }
}

What is wrong here?

Answer 1

I think your problem is in the prepare for segue method. If the view controller is on a navigation stack i think your code should be something like

 override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if let destinationViewController = segue.destination as? UINavigationController).topViewController as! secondViewController{
        destinationViewController.delegate = self
    }
}

Answer 2

This works me well.

1st VC

class ViewController: UIViewController, backfromSecond {

    override func viewDidLoad() {
        super.viewDidLoad()
    }
  @IBAction func Passingfrom1stVCTo2ndVC(_ sender: AnyObject) {
        if let vc = self.storyboard?.instantiateViewController(withIdentifier: "ViewController3") as? ViewController3{
            vc.dataFrom1StVC = "message send from 1st VC"
            vc.delegate = self
           self.navigationController?.pushViewController(vc, animated: true)
        }
    }
    func back(text: String) {
        print("data\(text)")
    }
    }

2nd VC.

protocol backfromSecond: class {
    func back(text: String)
}

class ViewController3: UIViewController {

    var dataFrom1StVC : String? = nil
    week var delegate : backfromSecond?
    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func DataSendFrom2ndVCTo1stVC(_ sender: AnyObject) {
        self.delegate?.back(text: "Message Send From 2nd vc to 1st VC")
        self.navigationController?.popViewController(animated: true)
    }
}

I hope it will work you. If any problem then ask me i will help you.

Answer 3

You can use unwind segues to pass data back. Here's a tutorial https://spin.atomicobject.com/2014/10/25/ios-unwind-segues/

Answer 4

Suppose A & B are two controllers and you first navigated from A to B with some data. And now you want to POP from B to A with some data.

Unwind Segues is the best and recommended way to do this. Here are the steps.

1. Open Am

2. define following method

   @IBAction func unwindSegueFromBtoA(segue: UIStoryNoardSegue) {

   }

3. open storyboard

4. Select B ViewController and click on ViewController outlet. press control key and drag to 'Exit' outlet and leave mouse here. In below image, selected icon is ViewController outlet and the last one with Exit sign is Exit Outlet.

5. You will see 'unwindSegueFromBtoA' method in a popup . Select this method .

6. Now you will see a segue in your view controler hierarchy in left side. You will see your created segue near StoryBoard Entry Piont in following Image.

7. Select this and set an identifier to it. (suggest to set the same name as method - unwindSegueFromBtoA)

8. Open Bm . Now, wherever you want to pop to A. use

   self.performSegueWithIdentifier("unwindSegueFromBtoA", sender: dataToSend)

9. Now when you will pop to 'A', 'unwindSegueFromBtoA' method will be called. In unwindSegueFromBtoA of 'A' you can access any object of 'B'.

10. That's it..!