Embedding Navigation Controller into Tab Bar Controller - ios

Question

I currently have a DetailViewController segued from a ViewController, which is embedded in a UINavigationViewController, which I want to embed in a UITabBarController. When I first did it on my storyboard, my app crashed with the error:
"Could not cast value of type 'UITabBarController' (0x10badf258) to 'UINavigationController' (0x10badf208)".
After research, I added the first two lines (let tabVc =, and let navVc = ) and still crashed. What am I missing to create a successful TabBarController?
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let tabVc = segue.destinationViewController as! UITabBarController
let navVc = tabVc.viewControllers!.first as! UINavigationController
if segue.identifier == "ShowItem" {
if let row = tableView.indexPathForSelectedRow?.row {
let item = itemStore.allItems[row]
let detailViewController = segue.destinationViewController as! DetailViewController
detailViewController.item = item
detailViewController.imageStore = imageStore
}
}
}
UPDATE: After applying changes, my error has changed to
"Could not cast value of type 'UITabBarController' (0x103ff6258) to 'Photomania.ItemsViewController' (0x1029520d0)."
Error

Answer 1

I think you are approaching the problem in a wrong way. You can set the imageStore and itemStore of ItemsViewController in it's viewDidLoad.
override func viewDidLoad() {
super.viewDidLoad()
self.itemStore = ItemStore()
self.imageStore = ImageStore()
}
But if you wish to do it in didFinishLaunchingWithOptions of AppDelegate then this is how you would do it.
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
// Override point for customization after application launch.
let rootController = window?.rootViewController
if rootController is UITabBarController {
let firstTabItem = (rootController as! UITabBarController).viewControllers?[0]
if firstTabItem is UINavigationController {
let firstController = (firstTabItem as! UINavigationController).viewControllers.first as! ItemsViewController
firstController.itemStore = ItemStore()
firstController.imageStore = ImageStore()
}
}
}

Answer 2

As the error clearly states, it's this line of code that is failing:
let navVc = tabVc.viewControllers!.first as! UINavigationController
according to the error the first viewController in the tabVC is not a navigationVC.
So make sure your tab bars are arranged in the correct order and be certain that the first viewController of your tabVC is indeed a navigation view controller.