Swift 4 - pass data from ViewController to a ViewController to a tab bar

Question

Here is my code:

MainViewControler

class LoginViewController: UIViewController {

    // outlets
    @IBOutlet weak var textFieldLogin: UITextField!
    @IBOutlet weak var textFieldPassword: UITextField!
    let cms = Connect()
    var loggedUser : LoginUser?

    @IBAction func btnLoginPressed(_ sender: Any) {
        if self.textFieldLogin.text?.isEmpty ?? true || self.textFieldPassword.text?.isEmpty ?? true  {
            self.errorLoginMessage(txt: "Uzupełnij wszystkie pola!!", title: "Błąd")
        } else {
            cms.checkUsersLogin(login: self.textFieldLogin.text, password: self.textFieldPassword.text, callback: { (data, error) in
                if error == nil{
                    if let dane = data {
                        do {
                            let decoder = JSONDecoder()
                            self.loggedUser = try decoder.decode(LoginUser.self, from: data!)

                            if ((self.loggedUser?.id ) == nil) {
                                let json = try? JSONSerialization.jsonObject(with: data!, options: [])

                                if let dictionary = json as? [String: Any] {
                                    if let komunikat = dictionary["komunikat"] as? String, let title = dictionary["error"] as? String {
                                        DispatchQueue.main.async {
                                            self.errorLoginMessage(txt: komunikat, title: title)
                                        }
                                    }
                                } else {
                                    DispatchQueue.main.async {
                                        self.errorLoginMessage(txt: "Podany login lub hasło jest błędny!!", title: "Błąd")
                                    }
                                }
                            } else {
                                DispatchQueue.main.async {
                                    self.performSegue(withIdentifier: "toLoginUser", sender: self)
                                }
                            }
                        }
                        catch {
                            print("Error in decoder")
                        }
                    } else {
                        print("Error 103: \(data)")
                    }
                } else {
                    print("Error 104: \(error)")
                }


            })
        }
    }




    override func viewDidLoad() {
        super.viewDidLoad()

    }


    override func prepare(for segue: UIStoryboardSegue, sender: Any?){
        if segue.identifier == "toLoginUser" {
            // access the second tab bar
            //let secondDes = barViewControllers.viewControllers?[1] as! SecondViewController
            //secondDes.test = "Hello TabBar 2"

            let storyboard = UIStoryboard(name: "Main", bundle: nil)
            let tabVC = storyboard.instantiateViewController(withIdentifier: "MainVC") as! UITabBarController
            self.present(tabVC, animated: true, completion: {
                let vc = tabVC.selectedViewController as! NewsViewController
                vc.loggedUser = self.loggedUser
            })

        }
    }


}

TabBarViewController:

class NewsViewController: UIViewController {

    var loggedUser : LoginUser?

    override func viewDidLoad() {
        super.viewDidLoad()
        print("Sprawdzam obiekt: \(loggedUser)")
        dump(loggedUser)
    }

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


    @IBAction func testBtnPressed(_ sender: Any) {
        print("Sprawdzam obiekt: \(self.loggedUser)")
        dump(self.loggedUser)
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self.tabBarController?.navigationItem.title = "Aktualności"
    }
    override var prefersStatusBarHidden: Bool {
        return true
    }
}

I create the correct object in MainViewControler, but when I open the TabbedViewControler - the data of this object are not visible.

Does anyone know why this is happening and how to fix this problem?

Answer 1

EDIT: I checked in my project where I have similar functionality, where I pass loggedUser object to next View Controller and I have something like this:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "toLoginUser" {
            let navCon = segue.destination as! UINavigationController
            let newsVC = navCon.topViewController as! NewsViewController
            if let user = sender as? NSManagedObject {
                newsVC.loggedUser = self.loggedUser
            }

        }
    }

Try using this without self.present() method, because View should be automatically presented. In my case this method works as you described in comments.