How to transfer array variables between tab bar controllers?

Question

I'm trying to understand the life cycle of view controllers. I need to use TabBar to switch controllers. And when switching controllers, I need the label to display life-cycle methods, not only of the controller on which I now find, but also from others.

I created an empty array private var arrayOfMethods = [String]() in which I add a triggered method every time.

class ViewController: UIViewController {

    private var arrayOfMethods = [String]()

    @IBOutlet var greenLabel: UILabel!
    @IBOutlet var blueLabel: UILabel!
    @IBOutlet var yellowLabel: UILabel!

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

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        printMessage()
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        printMessage()
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        printMessage()
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        printMessage()
    }

    func printMessage(line: Int = #line, function: String = #function) {
        print("\(title ?? "nil"). Line: \(line) of function \(function)")
        arrayOfMethods.append(function)
        let string = arrayOfMethods.joined(separator: "\n")
        greenLabel.text = "\(title ?? "nil") \(string)"
    }
}

Answer 1

You can create a common class and call its function from all of your view controllers

 class Helper: NSObject {

    private var arrayOfMethods = [String]()
    static let shared = Helper()
    let mainLabel = UITextView(frame: CGRect(x: 100, y: 100, width: 300, height: 300))

    private override init() {
        super.init()
    }

    func printMessage(vc: UIViewController, line: Int = #line, function: String = #function) {
        print("\(vc.title ?? "nil"). Line: \(line) of function \(function)")
        arrayOfMethods.append( (vc.title ?? "nil") + "-" + function)
        let string = arrayOfMethods.joined(separator: "\n")

        guard let window = UIApplication.shared.keyWindow else { return }

        if !window.subviews.contains(mainLabel) {
            window.addSubview(mainLabel)
            window.bringSubviewToFront(mainLabel)
        }
        mainLabel.text = string
    }
}

And call this singleton class method from all your view controllers like this

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        Helper.shared.printMessage(vc: self)
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        Helper.shared.printMessage(vc: self)
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        Helper.shared.printMessage(vc: self)
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        Helper.shared.printMessage(vc: self)
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        Helper.shared.printMessage(vc: self)
    }
}

Output