Swift - reloadData UITableView entering in Foreground - ios

Question

I would like to call reloadData method of TableView when i return in foreground. My TableView is built programmatically.
In FirstViewController i've the methods to populate the TableView and the function reloadListOfApps where i call reloadDatamethods.
class FirstViewController: UIViewController, UITableViewDataSource, UITableViewDelegate, MFMailComposeViewControllerDelegate {
#IBOutlet weak var listOfApps: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
listOfApps.delegate = self
listOfApps.dataSource = self
}
func reloadListOfApps() {
listOfApps.reloadData()
}
// ================ TABLE DELEGATE/MANAGER ===================
let apps = ListAppClass.listApp()
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return apps!.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = UITableViewCell()
let bundle = apps! [indexPath.row]
let bundle_temp = String(describing: bundle)
cell.textLabel?.text = bundle_temp
return cell
}
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
print("Current Cell!")
}
}
In AppDelegate i've
func applicationWillEnterForeground(_ application: UIApplication) {
// Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
FirstViewController().reloadListOfApps()
}
When i run the app i've this error
Fatal error: Unexpectedly found nil while unwrapping an Optional value
Reading some questions i've also check the Outlets in Storyboard, and seems all ok.
Hooks correspond to FirstViewController
Where is the error?

Answer 1

Try add oberver in your view controller
NotificationCenter.default.addObserver(self,
selector: #selector(applicationWillEnterForeground),
name: .UIApplicationWillEnterForeground,
object: nil)
callback
#objc func applicationWillEnterForeground() {
listOfApps.reloadData()
}
//// problem explaining
when you write this code in AppDelegate
FirstViewController().reloadListOfApps()
this creates an instance on the fly whose all properties are nil as you didn't load the storybaord object or Xib file associated with that is not presented away from the currently active one , control goes to reloadListOfApps function and find that listOfApps you want to reload is nil so crash happens , the solution above is one way , another way is to use delegate or make listOfApps a shared object that can be referenced anywhere