Injecting an object into UIViewController from AppDelegate - ios

Question

I am attempting to inject an object into a UIViewController from the AppDelegate but I am not sure that I am doing it correctly. Please can someone advise. I get an error when I start my application at the line of code marked 'THE ERROR OCCURS HERE'.
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
// Create ItemStore instance
let itemStoreObject = ItemStore()
let storyBoard: UIStoryboard = UIStoryboard.init(name: "Main", bundle: nil)
let testController = storyBoard.instantiateViewController(withIdentifier: "testTableController") as! TestTableViewController
testController.itemstore = itemStoreObject
return true
}
ItemStore:
import UIKit
class ItemStore {
var allItems = ["Thanh", "David", "Tommy", "Maria"]
}
TestTableViewController:
class TestTableViewController: UIViewController, UITableViewDelegate, UISearchBarDelegate, UITableViewDataSource{
#IBOutlet var myTableView: UITableView!
var itemstore: ItemStore!
override func viewDidLoad() {
super.viewDidLoad()
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
print("numberOfRowsSection ...")
return itemstore.allItems.count // THE ERROR OCCURS HERE.
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
print("cellForRow ...")
// Get a new or recycled cell
let cell = UITableViewCell(style: .value1, reuseIdentifier: "UITableViewCell")
let name = itemstore.allItems[indexPath.row]
cell.textLabel?.text = name
return cell
}
}
I get the following error message (marked in the line 'THE ERROR OCCURS HERE'):
fatal error: unexpectedly found nil while unwrapping an Optional value
(lldb)

Answer 1

You instantiate a view controller in AppDelegate, but the system will create another instance of that view controller class and hence display an instance of the class that has no itemstore property initialised.
You either have to make itemstore a type variable instead of an instance variable or if you only need this functionality for your root view controller, you have to instantiate the itemstore variable for your root view controller instance, which you know will be the one used by your navigation controller.