We'll be going over how to use UserDefaults to save data on the device today. Whenever a user logs in, we'll keep track of this information using a boolean and a key that we'll store inside of UserDefaults. Doing so will allow us a clean way to load our initial view based on the information we have about our user. As a bonus, let's go over a more robust way of saving things into UserDefaults by introducing an Enumeration for our string keys.

!codebreak <div class='filename'>LoginController.swift</div> !codebreak !syntax-highlight class LoginController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout, LoginControllerDelegate { //... func finishLoggingIn() { //we'll perhaps implement the home controller a little later let rootViewController = UIApplication.shared.keyWindow?.rootViewController guard let mainNavigationController = rootViewController as? MainNavigationController else { return } mainNavigationController.viewControllers = [HomeController()] UserDefaults.standard.setIsLoggedIn(value: true) dismiss(animated: true, completion: nil) } //... } filebreak:MainNavigationController class MainNavigationController: UINavigationController { //... fileprivate func isLoggedIn() -> Bool { return UserDefaults.standard.isLoggedIn() } //... } !codebreak <div class='filename'>HomeController.swift</div> !codebreak !syntax-highlight class HomeController: UIViewController { override func viewDidLoad() { //... navigationItem.leftBarButtonItem = UIBarButtonItem(title: "Sign Out", style: .plain, target: self, action: #selector(handleSignOut)) //... } func handleSignOut() { UserDefaults.standard.setIsLoggedIn(value: false) let loginController = LoginController() present(loginController, animated: true, completion: nil) } } filebreak:UserDefaults+helpers extension UserDefaults { enum UserDefaultsKeys: String { case isLoggedIn } func setIsLoggedIn(value: Bool) { set(value, forKey: UserDefaultsKeys.isLoggedIn.rawValue) synchronize() } func isLoggedIn() -> Bool { return bool(forKey: UserDefaultsKeys.isLoggedIn.rawValue) } }