unwindSegue could not pass data (Swift - Xcode) - ios

Question

I'm using UserDefaults to store and retrieve my data but I have no idea why when I perform an unwind segue, my userdefaults data could not be passed over to the next view controller but if i do a normal push segue, my userdefaults data could be seen in the next viewcontroller.
P.S: ONLY self.performSegue(withIdentifier: "unwindSegue", sender: nil) is the unwindSegue.
FirstViewController
#IBAction func Button1(_ sender: Any) {
var i: Int = 0
let randomNumber = arc4random_uniform(3) + 1
i = Int(randomNumber)
let alert = AlertController(title: "Congratualations", message: "You earned \(i) tokens!", preferredStyle: .alert)
alert.setTitleImage(UIImage(named: "token"))
// Add actions
alert.addAction(UIAlertAction(title: "Let's See!", style: UIAlertActionStyle.default, handler: { (action) in
var returnValue: Int = UserDefaults.standard.integer(forKey: "tokens")
returnValue = returnValue + i;
UserDefaults.standard.set(returnValue, forKey:"tokens")
self.performSegue(withIdentifier: "unwindSegue", sender: nil)
}))
if (returnValue != 30){
alert.addAction(UIAlertAction(title: "Continue Playing", style: UIAlertActionStyle.default, handler: { (action) in
var returnValue: Int = UserDefaults.standard.integer(forKey: "tokens")
returnValue = returnValue + i;
UserDefaults.standard.set(returnValue, forKey:"tokens")
self.performSegue(withIdentifier: "continue", sender: self)
}))
}
self.present(alert, animated: true, completion: nil)
}
SecondViewController
import UIKit
class TokenController: UIViewController {
#IBOutlet var tokens: UILabel!
#IBOutlet var minus1: UIButton!
#IBOutlet var minus2: UIButton!
var returnValue: Int = UserDefaults.standard.integer(forKey: "tokens")
override func viewDidLoad() {
super.viewDidLoad()
tokens.text = "x\(returnValue)"
}
#IBAction func unwindSegue(_ sender: UIStoryboardSegue) {
}

Answer 1

Because when you do a Push of a new ViewController, this is loaded into memory and it's method "ViewDidLoad" is called.
When you do an unwind segue , the previous ViewController is already in memory, so the viewDidLoad and all the initialization are not called and the labels and all the graphics are not updated.
This is not a problem, because you can access all the data you needed in the unwindSegue implementation through the variable sender. See this example:
 
func unwindToViewController(segue: UIStoryboardSegue) {
        let vc_source = segue.source as! SecondViewController
        self.myLabel.text! = vc_sorgente.myTextField.text!      
}

Answer 2

#Kinja Please refer this url to use unwind segue
Click here:- Perform action when segue is closed