Embedding Navigation Controller into Tab Bar Controller

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

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.

Answer 2

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()
        }
    }
}