Initial ViewController with Firebase bug fix - ios

Question

I've strange bug I cannot understand how to solve. When I set which ViewController should be opened depends if users is registered and I put this code in SceneDelegate I get black screen for a moment before appearing ViewController
import UIKit
import FirebaseAuth
class SceneDelegate: UIResponder, UIWindowSceneDelegate {
var window: UIWindow?
let storyBoard = UIStoryboard(name: "Main", bundle: nil)
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
guard let windowScene = (scene as? UIWindowScene) else { return }
window = UIWindow(frame: windowScene.coordinateSpace.bounds)
window?.windowScene = windowScene
if let user = Auth.auth().currentUser {
FirestoreService.shared.getUserData(user: user) { (result) in
switch result {
case .success(let muser):
let navigationController = self.storyBoard.instantiateViewController(withIdentifier: "Navigation") as! UINavigationController
let conroller = self.storyBoard.instantiateViewController(withIdentifier: "MainController") as! MainController
navigationController.viewControllers = [conroller]
self.window?.rootViewController = navigationController
case .failure(_):
let conroller = self.storyBoard.instantiateViewController(withIdentifier: "SignUpController") as! SignUpController
self.window?.rootViewController = conroller
}
}
} else {
print(3)
let conroller = storyBoard.instantiateViewController(withIdentifier: "SignUpController") as! SignUpController
self.window?.rootViewController = conroller
}
window?.makeKeyAndVisible()
}
But when I put code for appearing ViewController outside the firebase it works as it should. How this can be fixed?

Answer 1

I think there are 2 ways to solve this issue.
1. Using a splash screen:
Don't make the decision of showing a login screen or main screen in scene(_:, session, connectionOptions). Instead, create a new view controller called SplashScreenViewController. Set your app's logo in its center. And then in its viewDidLoad() move your logic to check if the user is already logged in:
func chooseAndPresentStartScreen() {
let storyBoard = UIStoryboard(name: "Main", bundle: nil)
if let user = Auth.auth().currentUser {
FirestoreService.shared.getUserData(user: user) { (result) in
switch result {
case .success(let muser):
let navigationController = storyBoard.instantiateViewController(withIdentifier: "Navigation") as! UINavigationController
let conroller = storyBoard.instantiateViewController(withIdentifier: "MainController") as! MainController
navigationController.viewControllers = [conroller]
self.present(navigationController, animated: true, completion: nil)
case .failure(_):
let conroller = storyBoard.instantiateViewController(withIdentifier: "SignUpController") as! SignUpController
self.present(conroller, animated: true, completion: nil)
}
}
} else {
print(3)
let conroller = storyBoard.instantiateViewController(withIdentifier: "SignUpController") as! SignUpController
self.present(conroller, animated: true, completion: nil)
}
}
2. Using User Defaults:
Define a global variable for the key used to save user default value.
let isUserLoggedInKey: String = "IsUserLoggedIn"
After the user logs-in:
let defaults = UserDefaults.standard
defaults.setValue(true, forKey: isUserLoggedInKey)
Then in your scene(_:, session, connectionOptions), check if this value is set.
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
guard let windowScene = (scene as? UIWindowScene) else { return }
window = UIWindow(frame: windowScene.coordinateSpace.bounds)
window?.windowScene = windowScene
let defaults = UserDefaults.standard
let isLoggedIn = defaults.bool(forKey: isUserLoggedInKey)
if isLoggedIn {
let navigationController = self.storyBoard.instantiateViewController(withIdentifier: "Navigation") as! UINavigationController
let conroller = self.storyBoard.instantiateViewController(withIdentifier: "MainController") as! MainController
navigationController.viewControllers = [conroller]
self.window?.rootViewController = navigationController
} else {
let conroller = self.storyBoard.instantiateViewController(withIdentifier: "SignUpController") as! SignUpController
self.window?.rootViewController = conroller
}
window?.makeKeyAndVisible()
}
Don't forget to set isLoggedInKey to false when the user logs out.
let defaults = UserDefaults.standard
defaults.setValue(false, forKey: isUserLoggedInKey)
If you don't want to manually save value for isUserLoggedInKey when the user logs in and logs out, you can also use a state change listener. It takes a callback that is triggered when the user logs in or logs out. Add this in your Login view controller:
Auth.auth().addStateDidChangeListener { (auth, user) in
let defaults = UserDefaults.standard
defaults.setValue(user != nil, forKey: isUserLoggedInKey)
}