Receive SIGABRT error when trying to hijack root view controller - swift

Question

I am trying to have my application open a different view controller based upon whether an array is empty in the user's NSUserDefaults. Essentially, if the user has previously saved data in the app, the app will open up to where they can select the data. Otherwise, the app will open to a welcome screen.
However, when the array is empty, I see the background color that I set for the welcome screen, but not the text or button that I laid out in the storyboard. When the array is not empty and the data page should open, my app crashes with a SIGABRT error. I checked all of the outlets for the view controller in question and nothing seems to be disconnected. Additionally, when I comment out the code in the app delegate and set the data view controller as my initial starting view, the app runs fine.
The full error is "Thread 1: signal SIGABRT" and it is tagged in the class AppDelegate line.
The code I used in the App Delegate is below:
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
var accounts = loadAccounts()!
if accounts.isEmpty {
let welcomeController = WelcomeViewController()
self.window!.rootViewController = welcomeController
} else {
let tableController = AccountTableViewController()
self.window!.rootViewController = tableController
}
return true
}
func loadAccounts() -> [Account]? {
return NSKeyedUnarchiver.unarchiveObject(withFile: Account.ArchiveURL.path) as? [Account]
}

Answer 1

Maybe the UIWindow is not set properly.
let bounds = UIScreen.main.bounds
self.window = UIWindow(frame: bounds)
self.window?.rootViewController = `your view controller`
self.window?.makeKeyAndVisible()
What else can go wrong?
var accounts = loadAccounts()!
This line is the culprit for you. Precisely this symbol ! is I guess. You are trying to fetch data from a database or a filesystem and expect it will always be there.
Think about it, it can't be true all the time.
# check if account array is not empty; I would have returned nil if it would be empty and so we can avoid that extra check here.
if let accounts = loadAccounts(), !accounts.isEmpty {
let tableController = AccountTableViewController()
self.window!.rootViewController = tableController
return true
}
let welcomeController = WelcomeViewController()
self.window!.rootViewController = welcomeController
Also, if you can provide more info about the error message from your debug console. Then I would be able to help in a better way.