Set rootViewController in AppDelegate (Before iOS 13 and Xcode 11)

AppDelegate.swift

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    
    var window: UIWindow?
    
    func application(_ application: UIApplication,
                     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Create a new window property 
        self.window = UIWindow(frame: UIScreen.main.bounds)
        
        // Set custom LoginViewController as root
        self.window?.rootViewController = LoginViewController()
        
        // Present the window
        self.window?.makeKeyAndVisible()
        return true
    }
}