How to add data to the tableView and reload? - ios

Question

I'm trying to add a cell to a tableView that's in viewController by sending data via a segue from another viewController.
class FavoritesViewController: UIViewController {
var shops = [
"hello world",
"hello world",
"hello world"
]
#IBOutlet weak var table: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
table.delegate = self
table.dataSource = self
table.reloadData()
}
}
//protocol FavoritesDelegate: class {
// func add(_ shopName: String)
//}
extension FavoritesViewController: UITableViewDelegate, UITableViewDataSource{
func add(_ shopName: String) {
print(shopName)
shops.append(shopName)
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return shops.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell",for: indexPath)
cell.textLabel?.text = shops[indexPath.row]
return cell
}
// define the action. In this case "delete"
func tableView(_ tableView: UITableView, editingStyleForRowAt indexPath: IndexPath) -> UITableViewCell.EditingStyle {
return .delete
}
// do the actual deleting
func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
tableView.beginUpdates()
shops.remove(at: indexPath.row)
tableView.deleteRows(at: [indexPath], with: .fade)
tableView.endUpdates()
}
}
}
And here's the function call in the other viewController (prepare):
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
favoritesDestinationVC = segue.destination as! FavoritesViewController
favoritesDestinationVC.add(shopName!)
}
I know what's causing the error (favoritesDestinationVC creates a new instance where tableView is nil), but I don't know how to solve it. Any ideas on how I could add an entry to the tableView that way (and updating the table afterwards) without my app crashing?

Answer 1

Make your shops var public and then in the segue prepare callback use it directly. Check a variable first whether it has a valid value other than the nil, if it does then proceed to avoid crashes. You can do it using an if statement to verify as you can see in the sample code. Or you can use optionals to avoid crashes. See the code below.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.destination is FavoritesViewController {
let destinationVC = segue.destination as? FavoritesViewController // Use optionals which has ? (question mark)
// To avoid crashes check if shopName has a valid value other than nil
if let newShopName = shopName {
// It is possible that the "shopName" has a nil value when the program reaches here.
// That's why we will use the verified "newShopName" instead of "shopName" itself to avoid any crash.
destinationVC?.shops.append(newShopName) // What I recommend, if not convenient for you just delete this line,
// destinationVC?.add(newShopName) // after deleting the recommended line, uncomment this line for your convenience.
}
}
}