Presenting different UIViewController on the app Launch - ios

Question

I need to present different UIViewController on the launch of my app. I have a "login" page for the user to interact with. Once the user logs in or creates an account it takes to a different UIViewController with a map to interact with. I've looked online and so far I know that we should do it within AppDelegate.swift file. I have not completed the statement whether or not the user has logged in since I am still running into some errors
AppDelegate
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
Thread.sleep(forTimeInterval: 2.0)
window = UIWindow(frame: UIScreen.main.bounds)
window?.makeKeyAndVisible()
window?.rootViewController = MainNavigationContoller()
return true
}
I also have another swift file with MainNavigationContoller that should call the mainviewController
override func viewDidLoad() {
super.viewDidLoad()
let isloggedIn = false
if isloggedIn == false {
self.present(mainViewController(), animated: true, completion: nil)
} else {
self.present(mapViewController(), animated: true, completion: nil)
}
}
The app launches with the launchScreen but then sends errors to mainViewController such as Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

Answer 1

You are not instantiating the View Controllers properly.
Here is a function that I use to make a root view controller, put this into your AppDelegate.
func makeRootVC(storyBoardName : String, vcName : String) {
let vc = UIStoryboard(name: storyBoardName, bundle: Bundle.main).instantiateViewController(withIdentifier: vcName)
let nav = UINavigationController(rootViewController: vc)
nav.navigationBar.isHidden = true
self.window?.rootViewController = nav
let options: UIView.AnimationOptions = .transitionCrossDissolve
let duration: TimeInterval = 0.6
UIView.transition(with: self.window!, duration: duration, options: options, animations: {}, completion: nil)
}
Now in your Appdelegate, replace your code with this:
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
Thread.sleep(forTimeInterval: 2.0)
self.makeRootVC(storyboardName: "Main", vcName : "YourVCStoryboardId")
return true
}
and in your MainNavigationController,
override func viewDidLoad() {
super.viewDidLoad()
let isloggedIn = false
let appDelegateObj = UIApplication.shared.delegate as! AppDelegate
if isloggedIn == false {
appDelegateObj.makeRootVC(storyboardName: "Main", vcName: "mainViewController")
} else {
appDelegateObj.makeRootVC(storyboardName: "Main", vcName: "mapViewController")
}
}
NOTE: Open storyboard and give every controller a StoryboardID. What I prefer is naming them the same as ViewController's name as it is easy to remember. and in vcName, we need to pass the storyboarID of the controller we want to present.
UPDATE:
Above code is for making a root view controller, if you want to push controllers, you can use this code instead:
extension UIViewController {
func pushVC(storyboardName : String, vcname : String) {
let vc = UIStoryboard.init(name: storyboardName, bundle: Bundle.main).instantiateViewController(withIdentifier: vcname)
vc.hidesBottomBarWhenPushed = true
self.navigationController?.pushViewController(vc, animated: true)
}
}
In your MainNavigationController if instead of making root view controllers in viewDidLoad, you want to just push the controller, then use the above code like this:
override func viewDidLoad() {
super.viewDidLoad()
let isloggedIn = false
if isloggedIn == false {
self.pushVC(storyboardName: "Main", vcName: "mainViewController")
} else {
self.pushVC(storyboardName: "Main", vcName: "mapViewController")
}
}