Swift view appears to delay being loaded into window hierarchy - swift

Question

A very strange thing is happening, it appears my initial view controller loads up, performs its logic and all but the actual view itself isn't added to the hierarchy until everything else happens.
protocol OnboardDisplayLogic: class
{
func handleUserConfirmation(viewModel: OnboardModels.CheckForUser.ViewModel)
}
class OnboardViewController: UIViewController, OnboardDisplayLogic {
var interactor: OnboardInteractor?
var router: (NSObjectProtocol & OnboardRoutingLogic & OnboardDataPassing)?
override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
setup()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
setup()
}
//MARK: Setup
private func setup() {
let viewController = self
let interactor = OnboardInteractor()
let presenter = OnboardPresenter()
let router = OnboardRouter()
viewController.interactor = interactor
viewController.router = router
interactor.presenter = presenter
presenter.viewController = viewController
router.viewController = viewController
router.dataStore = interactor
}
private func setupView() {
view.backgroundColor = UIColor.brown
}
//MARK: Routing
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let scene = segue.identifier {
let selector = NSSelectorFromString("routeTo\(scene)WithSegue:")
if let router = router, router.responds(to: selector) {
router.perform(selector, with: segue)
}
}
}
//MARK: View lifecycle
override func viewDidLoad() {
super.viewDidLoad()
setupView()
interactor?.checkForUser()
}
func handleUserConfirmation(viewModel: OnboardModels.CheckForUser.ViewModel) {
if let username = viewModel.username {
print("Logged in user: \(username)")
router?.routeToUserFeed(segue: nil)
} else {
print("No user logged in")
router?.routeToLoginRegister(segue: nil)
}
}
The reason I think it's delayed is that although I've set the view background colour to brown, using breakpoints at the print("user not logged in") code I get that printed to console, because there is no user logged in as determined the Interactor, but view remains white. It's not until I step over and complete running all the code does the screen then become brown.
Therefore I'm getting the error
Warning: Attempt to present ... whose view is not in the window
hierarchy!
as something is preventing the view from being added until the very end.

Answer 1

Actual views aren't loaded until they enter the view controller lifecycle.
If you need to load the view to setup before it's added to a superview's hierarchy, just use the getter of the view (let _ = viewController.view).
UIViewControllers also have the loadView() method, check it out: Apple documentation.
We've also had these kind of problems with Clean Swift. The correct way of working would be to instantiate from the storyboard and just use normal segues/lifecycle, just as MVC does for Apple examples.
Instead of doing let viewControllerToPush = MyVCSublass(...), you should instantiate from storyboard let viewControllerToPush = storyboard?.instantiate... and use that view controller.