Why is this variable not printing in this function? - ios

Question

When ViewController loads, the correct value gets printed. But when tried to print the same value with a UIButton, the print is nil
ViewController
var userEmail: String?
func userLoggedIn(data: String) {
userEmail = data //sent from delagate
print(userEmail) // successfully printed
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "loginView" {
let loginViewController: LoginViewController = segue.destination as! LoginViewController
loginViewController.delegate = self
}
}
override func viewDidAppear(_ animated: Bool) {
let isUserLoggedIn = UserDefaults.bool(UserDefaults.standard)(forKey: "isUserLoggedIn")
if(!isUserLoggedIn) {
self.performSegue(withIdentifier: "loginView", sender: self);
}
}
#IBAction func createCommunityTapped(_ sender: AnyObject) {
let createCommunityController = self.storyboard?.instantiateViewController(withIdentifier: "CreateNewCommunity") as! CreateNewCommunity
print ("now here ", userEmail) // prints nil
createCommunityController.myEmail = userEmail
}
The userEmail value is being passed from LoginViewController via this section of code:
if(returnValue != "error") {
self.delegate?.userLoggedIn(data: userEmail! )
UserDefaults.set(UserDefaults.standard)(true, forKey: "isUserLoggedIn");
let mainPage = self.storyboard?.instantiateViewController(withIdentifier: "ViewController")
let mainPageNav = UINavigationController(rootViewController: mainPage!)
let appDelegate = UIApplication.shared.delegate
appDelegate?.window??.rootViewController = mainPageNav
self.dismiss(animated: true, completion: nil)
}
AppDelegate:
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
// Override point for customization after application launch.
let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let isUserLoggedIn = UserDefaults.bool(UserDefaults.standard)(forKey: "isUserLoggedIn")
if(!isUserLoggedIn) {
let loginViewController = mainStoryboard.instantiateViewController(withIdentifier: "LoginViewController")
self.window?.rootViewController = loginViewController
window!.makeKeyAndVisible()
} else {
let protectedPage = mainStoryboard.instantiateViewController(withIdentifier: "ViewController")
self.window?.rootViewController = protectedPage
window!.makeKeyAndVisible()
}
return true
}

Answer 1

The issue seems to lie in your Login view controller. You're passing the userEmail to your first instance of ViewController, then creating a new instance of ViewController and setting it as the root, which releases the first one. The first step should be to remove this code:
let mainPage = self.storyboard?.instantiateViewController(withIdentifier: "ViewController")
let mainPageNav = UINavigationController(rootViewController: mainPage!)
let appDelegate = UIApplication.shared.delegate
appDelegate?.window??.rootViewController = mainPageNav
In your AppDelegate, you should set the root view controller to ViewController, and modally present the LoginViewController on top of it if the user is not logged in. Make sure to set the LoginViewController's delegate to ViewController. Then your login logic can be:
if(returnValue != "error") {
self.delegate?.userLoggedIn(data: userEmail!)
UserDefaults.standard.set(true, forKey: "isUserLoggedIn")
self.dismiss(animated: true, completion: nil)
}