How to make segue pass string works?

Question

I am trying a segue to pass a string from a view controller to another view controller but it's not working.

Xcode 10, Swift 4, iOS 10.

viewcontroller.swift code:

import UIKit

class ViewController: UIViewController {
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "segue_vc_to_myvc" {
            let vc = segue.destination as! MyViewController
            vc.str = "hello"
        }
    }
}

Myviewcontroller.swift:

import UIKit

class MyViewController: UIViewController {
    @IBOutlet weak var label:UILabel!

    var str: String? = nil

    override func viewDidLoad() {
        super.viewDidLoad()
        //label.text = str
        if let str = str {
            print(str)
        }
    }

I want to show the string on screen, but it's nothing. I tried to use a label and it still has nothing.

If I use label.text = str, the error messages is:

self    _0190603.MyViewController   0x000000010130a490
UIKit.UIViewController  UIViewController    
label   UILabel?    nil none
str String? nil none

set the break point and error message

segue.identifier

the label have nothing...

are you sur you go through `if segue.identifier == "segue_vc_to_myvc" { }`statement ? double check your segue identifier — Olympiloutre, Jun 04 '19 at 02:41
It looks as if your UILabel outlet is not connected in the Storyboard (and the problems is unrelated to passing data between view controllers). — Martin R, Jun 04 '19 at 02:56
set a breakpoint at vc.str=.... get the error message is : Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value — Angeloli, Jun 04 '19 at 03:34
i update 3 pics in my post, you can help me to check it, thanks. — Angeloli, Jun 04 '19 at 06:28

score 0 · Answer 1 · answered Jun 04 '19 at 03:29

In your storyboard check the Segue's identifier between the two page.

then make sure you trigger the right way to preform the segue.

something like this

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

add a break point at 'if segue.identifier == blablabla' and see what happening here

   override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "second_page" {
            let page = segue.destination as! SecondeViewController
            page.txt = "hello world"
        }
    }

the identifier is "segue_vc_to_myvc". – Angeloli Jun 04 '19 at 05:40 — Angeloli, Jun 04 '19 at 05:40

score 0 · Answer 2 · answered Jun 04 '19 at 05:07

0

check whether you have set the identifier correctly. It should work as it is!

answered Jun 04 '19 at 05:07

The Pedestrian

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2
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i can't add comment with photo. and my identifier is "segue_vc_to_myvc". – Angeloli Jun 04 '19 at 05:41
Try deleting the segue and adding a fresh one. Sometimes it helps! – The Pedestrian Jun 04 '19 at 06:11
Also check whether you have used the same segue identifier for some other segue perhaps? – The Pedestrian Jun 04 '19 at 06:16
I have try it and still the same. – Angeloli Jun 04 '19 at 06:29

How to make segue pass string works?

2 Answers2