Can't pass values in UIStoryBoard segue

Question

I need to send bool value to Second viewController based on some condition. but in Second ViewController the value of bool variable is always false. This is First ViewController code:

import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}
@IBAction func moveTo(_ sender: Any) {
    self.performSegue(withIdentifier: "Move2", sender: self)

}
override func prepare(for segue: UIStoryboardSegue, sender: Any?)
{
    if segue.identifier == "Move2"
    {
        let secondVC = segue.destination as? SecondViewController
        secondVC?.second = true

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

The SecondViewController code is

import UIKit

class SecondViewController: UIViewController {
var second = Bool()

override func viewDidLoad() {
    super.viewDidLoad()
    print(second)
    // Do any additional setup after loading the view.
}

But this Value of second variable is false.

Whats wrong in my code. need help. TIA..

EDIT : In both ViewController i have navigation controller. That's problem. SecondVC is SecondViewController's navigation controller, so that i can't pass data to that secondVC.

Did you set the segue identifier in Storyboard? Click the segue arrow and in the identify inspector set the segue identifier as `Move2` — Alejandro Iván, Apr 11 '18 at 13:34
Make sure the `class` of your `SecondViewController` has been set in the Storyboard. — vacawama, Apr 11 '18 at 13:34
keep a break point at *secondVC?.second = true* line. and debug is compiler stops here. — MRizwan33, Apr 11 '18 at 13:36
Stick a print under `secondVC?.second = true` to check that `secondVC` is not nil and in fact held this assignment. — bauerMusic, Apr 11 '18 at 13:36
Well there you go. That's you issue. This means, `secondVC` is nil. That means, the VC you're getting is not what you think. Try to see it in the debugger — bauerMusic, Apr 11 '18 at 13:45
So value isnt passed from previous view controller. Did you use breakpoints in prepareforsegue method? — RajeshKumar R, Apr 11 '18 at 13:47
The segue is working. It seems that the ViewController is not `SecondViewController` class. — bauerMusic, Apr 11 '18 at 13:49
Try: `print(String(describing: segue.destination))` See what class is the VC you're getting. — bauerMusic, Apr 11 '18 at 13:53
print(segue.destination) and check destination view controller class name — RajeshKumar R, Apr 11 '18 at 13:55
in both viewcontroller it contains Navigation Controller. I removed navigation Controller in second VC. now its working fine.. is that problem? — Vimalkumar N.M., Apr 11 '18 at 13:56
Have you drag your segue from ViewController or from Button. — Kazi Abdullah Al Mamun, Apr 11 '18 at 13:57
Then it should work, maybe problem was with navController what you mentioned above comment. — Kazi Abdullah Al Mamun, Apr 11 '18 at 14:00
Check the duplicate for how to pass data through a UINavigationController. — vacawama, Apr 11 '18 at 14:05

score 1 · Answer 1 · answered Apr 11 '18 at 13:53

1

Go to your Storyboard and select SecondViewController (the yellow circle on the top left. Go to identity inspector and select SecondViewController from the Class drop down.

See image below:

answered Apr 11 '18 at 13:53

Martin Muldoon

3,388
4
24
55

in both viewcontroller it contains Navigation Controller. I removed navigation Controller in second VC. now its working fine.. is that problem? – Vimalkumar N.M. Apr 11 '18 at 13:57
If the SecondViewController was embedded in a Navigation Controller it would cause an issue. Typically your First VC is embedded and that's it. – Martin Muldoon Apr 11 '18 at 14:02

score 0 · Answer 2 · answered Apr 11 '18 at 13:43

0

Keep things simple and clean :

FirstVC :

override func prepare(for segue: UIStoryboardSegue, sender: Any?)
    {
        if segue.identifier == "Move2"
        {
            let secondVC = segue.destination as? SecondViewController
            secondVC.second = true

        }
    }

SecondVC :

class SecondViewController: UIViewController {
    var second: Bool = false

    override func viewDidLoad() {
        super.viewDidLoad()
        print(second)
    }  
}

Just tested this myself. true is printed.

answered Apr 11 '18 at 13:43

Nitish

13,845
28
135
263

`secondVC?.second = true` - Is optional – Scriptable Apr 11 '18 at 13:44
How about `if let secondVC = ...`, `secondVC` is an optional. – bauerMusic Apr 11 '18 at 13:44
@Scriptable : I don't see any need for optional. – Nitish Apr 11 '18 at 13:45
2

`let secondVC = segue.destination as? SecondViewController` as? creates optional – Scriptable Apr 11 '18 at 13:46
You can change `as?` to `as!` which is a perfectly valid coding decision. You'd want it to crash if you didn't have the segue wired to the correct VC type. – vacawama Apr 11 '18 at 13:47
@Scriptable : Have you tried that ? There is **no** need of taking that optional in secondVC?.second = true – Nitish Apr 11 '18 at 13:47
@vacawama I have to disagree, allowing a crash is not a valid coding decision – Scriptable Apr 11 '18 at 13:49
@Scriptable, not having your segue wired to the correct type is a programming error not a runtime error. It's the same as not wiring up an outlet. You want that to crash so that you find the problem. – vacawama Apr 11 '18 at 13:51
@Nitish its not a big deal, just trying to help improve your answer. `let vc = SecondViewController() let secondVC = vc as? SecondViewController print(secondVC)` prints an optional. xcode autocorrects `secondVC.second = true` to `secondVC?.second = true` try it – Scriptable Apr 11 '18 at 13:52
You cannot have `as?` casting returning a non optional. – bauerMusic Apr 11 '18 at 13:57
in both viewcontroller it contains Navigation Controller. I removed navigation Controller in second VC. now its working fine.. is that problem? – Vimalkumar N.M. Apr 11 '18 at 13:58
@VimalkumarN.M. No it shouldn't cause any issues unless you need a nav controller there – Scriptable Apr 11 '18 at 14:00
@Nitish @Scriptable what is the differences between `var myBool = Bool()` and `var myBool = false` both are initialized with false boolean value. – Kazi Abdullah Al Mamun Apr 11 '18 at 14:04
@Scriptable, if he has used `as!`, it would have crashed saying `UINavigationController` couldn't be cast as `SecondViewController` and we would have solved this bug in 30 seconds. – vacawama Apr 11 '18 at 14:08
@KaziAbdullahAlMamun nothing, myBool: Bool() is invalid though. vacamama agreed we would of got to the issue quicker. I use Swiftlint and validate my code style to that. https://github.com/realm/SwiftLint/blob/master/Rules.md#force-unwrapping – Scriptable Apr 11 '18 at 14:12

Can't pass values in UIStoryBoard segue

2 Answers2