when need to switch the rootViewController - ios

Question

I've been working on a Swift project and I have two view controllers, the login view controller & the home view controller. When a user launches the app, I want to display the login view controller if the user is not logged in, on the other hand, if the user is logged in, I want to display the home view controller.
So the flow is gonna be something like this.
When the user is not logged in, display
LoginViewController
HomeViewController
When the user is already logged in, display
HomeViewController
In the scene delegate, I've written
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
guard let scene = (scene as? UIWindowScene) else { return }
window = UIWindow(frame: scene.coordinateSpace.bounds)
window?.windowScene = scene
window?.rootViewController = HomeViewController() or LoginViewController() depending on the user's login status
window?.makeKeyAndVisible()
}
I was wondering if I should apply the HomeViewController as a rootviewcontroller regardless of the user's login status (and maybe present loginVC on the homeVC when the user is not logged in), or I should switch the view controller depending on the user's login status.
So, in this case, what is the point of switching rootviewcontroller? and why it is (or isn't important) to switch the root view controller?
Is there anything I should consider when I apply view controller to the root viewcontroller property?

Answer 1

// SceneDelegate.swift
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
// Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
// If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
// This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
guard let _ = (scene as? UIWindowScene) else { return }
// if user is logged in before
if let loggedUsername = UserDefaults.standard.string(forKey: "username") {
window?.rootViewController = HomeViewController()
} else {
// if user isn't logged in
window?.rootViewController = LoginViewController()
}
}

Answer 2

I think there can be another cases, like RootVC is a container ViewContoller consists of HomeVC and LoginVC.
example)
final class RootVC: UIViewController {
private let loginVC = LoginVC()
private let homeVC = HomeVC()
override func viewDidLoad() {
super.viewDidLoad()
addChild(homeVC)
view.addSubview(homeVC.view)
addChild(loginVC)
view.addSubview(loginVC.view)
}
func showVC() {
if isLogin {
homeVC.hide()
loginVC.show()
} else {
reverse()
}
}
}

Answer 3

Hi all i have one idea for set a RootViewController in SceneDelegate. First we need to create the method setViewController and variable currentScene in SceneDelegate class kindly feel free to refer the code below.
Two different viewcontroller as per your example HomeViewController, LoginViewController
import UIKit
class SceneDelegate: UIResponder, UIWindowSceneDelegate {
var window: UIWindow?
var currentScene: UIScene?
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
guard let _ = (scene as? UIWindowScene) else { return }
currentScene = scene
if UserDefaults.standard.bool(forKey: "isLoggedIn") == true{
self.setRootViewController(LoginViewController())
}else{
self.setRootViewController(HomeViewController())
}
}
func setRootViewController(_ viewController: UIViewController){
guard let scene = (currentScene as? UIWindowScene) else { return }
window = UIWindow(frame: scene.coordinateSpace.bounds)
window?.windowScene = scene
window?.rootViewController = viewController
window?.makeKeyAndVisible()
}
}
class ButtonViewController: UIViewController {
lazy var button: UIButton! = {
let button = UIButton()
button.translatesAutoresizingMaskIntoConstraints = false
button.backgroundColor = .darkGray
button.setTitleColor(.white, for: .normal)
button.addTarget(self, action: #selector(buttonAction), for: .touchUpInside)
button.tag = 1
button.setTitle("Tap", for: .normal)
return button
}()
override func loadView() {
super.loadView()
self.view.backgroundColor = .white
setConstraint()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
}
func setConstraint(){
self.view.addSubview(self.button)
NSLayoutConstraint.activate([
self.button.heightAnchor.constraint(equalToConstant: 60),
self.button.widthAnchor.constraint(equalToConstant: UIScreen.main.bounds.width * 0.66),
self.button.centerXAnchor.constraint(equalTo: self.view.centerXAnchor),
self.button.centerYAnchor.constraint(equalTo: self.view.centerYAnchor),
])
}
#objc func buttonAction(){ }
}
class HomeViewController: ButtonViewController{
override func loadView() {
super.loadView()
self.view.backgroundColor = .red
self.button.setTitle(String(describing: HomeViewController.self), for: .normal)
}
override func buttonAction() {
let sceneDelegate = UIApplication.shared.connectedScenes.first?.delegate as! SceneDelegate
sceneDelegate.setRootViewController(LoginViewController())
}
}
class LoginViewController: ButtonViewController{
override func loadView() {
super.loadView()
self.view.backgroundColor = .green
self.button.setTitle(String(describing: LoginViewController.self), for: .normal)
}
override func buttonAction() {
let sceneDelegate = UIApplication.shared.connectedScenes.first?.delegate as! SceneDelegate
sceneDelegate.setRootViewController(HomeViewController())
}
}
If click the button view controller can be change as rootViewController.
Output: