How do I keep track of elements of an array on two separate view controllers?

Question

Im developing a quiz app and on the first UIViewController the user is asked a question and given four buttons to press as answers. If they get the answer correct, that element is removed from the array of questions to be asked. However if I implement a segue to another view controller that asks the user if they want to continue when it segues back to the first view controller to ask another question the array is refilled with questions the user has already answered even though they are supposed to be removed. How can I make sure once I segue to the and from the second viewcontroller that asks the user if they want to continue that the array of questions doesn't refill with already answered questions?

Here is my code:

import UIKit

class ViewController: UIViewController {

var questionList = [String]()

func updateCounter() {

    counter -= 1
    questionTimer.text = String(counter)

    if counter == 0 {
        timer.invalidate()
        wrongSeg()
        counter = 15
    }
}


func randomQuestion() {

    //random question
    if questionList.isEmpty {
        questionList = Array(QADictionary.keys)
        questionTimer.text = String(counter)

    }

    let rand = Int(arc4random_uniform(UInt32(questionList.count)))
    questionLabel.text = questionList[rand]

    //matching answer values to go with question keys
    var choices = QADictionary[questionList[rand]]!

    questionList.remove(at: rand)


    //create button
    var button:UIButton = UIButton()

    //variables
    var x = 1
    rightAnswerBox = arc4random_uniform(4)+1

        for index in 1...4 {

            button = view.viewWithTag(index) as! UIButton
            if (index == Int(rightAnswerBox)){
                button.setTitle(choices[0], for: .normal)
            }
            else {
                button.setTitle(choices[x], for: .normal)
                x += 1
            }

            randomImage()
        }
    }


let QADictionary = ["Who is Thor's brother?" : ["Atum", "Loki", "Red Norvell", "Kevin Masterson"], "What is the name of Thor's hammer?" : ["Mjolinr", "Uru", "Stormbreaker", "Thundara"], "Who is the father of Thor?" : ["Odin", "Sif", "Heimdall", "Balder"]]

//wrong view segue
func wrongSeg() {
   performSegue(withIdentifier: "incorrectSeg", sender: self)
}

//proceed screen
func rightSeg() {
    performSegue(withIdentifier: "correctSeg", sender: self)
}
        //variables
var rightAnswerBox:UInt32 = 0
var index = 0

//Question Label
@IBOutlet weak var questionLabel: UILabel!

//Answer Button
@IBAction func buttonAction(_ sender: AnyObject) {

if (sender.tag == Int(rightAnswerBox) {
    //rightSeg()
    print ("Correct!")
}
    if counter != 0 {
        counter = 15
        questionTimer.text = String(counter)
    }
else if (sender.tag != Int(rightAnswerBox)) {
    wrongSeg()
print ("Wrong!")
    timer.invalidate()
    questionList = []

    }
   randomQuestion()
}

override func viewDidAppear(_ animated: Bool) {
randomQuestion()
}

//variables
var counter = 15
var timer = Timer()
@IBOutlet weak var questionTimer: UILabel!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    timer = Timer.scheduledTimer(timeInterval: 1, target:self, selector: #selector(ViewController.updateCounter), userInfo: nil, repeats: true)
        }

Code for second view controller:

import UIKit

class ContinueScreen: UIViewController {    
//correct answer label
@IBOutlet weak var correctLbl: UILabel!
//background photo
@IBOutlet weak var backgroundImage: UIImageView!

func backToQuiz() {
    performSegue(withIdentifier: "continueSeg", sender: self)
}

@IBAction func `continue`(_ sender: Any) {
    backToQuiz()
}

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

Answer 1

You will need to implement delegates for that. You can find more information here.

Your question is related to this.

Please go through that. Hope that helps.

Answer 2

The problem is that you - when you return to the first view controller in backToQuiz() - call performSegue, which will then

• create a new instance of the first view controller and
• re-initialize it with the original (unmodified) quiz data

Instead, you should do something like

func backToQuiz() { 
   if let nav = self.navigationController {
        nav.popViewController(animated: true)
    } else {
        self.dismiss(animated: true, completion: nil)
    }
}

to return to the parent view controller instance.