How to store and retrieve tabledata using userdefault Swift 4 - ios

Question

My task is user data appending into items array with strut method and assigning to tableView tableData array. In my code multiple places I used tableData for some validations.
Now, my problem is I can able to see my table data when I move background to foreground but If I remove application from background then again If I am open my application, There is empty tableView. So, I need to understand. how tableData store into UserDeafult and then retrieve to load tableView for avoid data loss.
// Array declaration
var items = [Item]()
var tableData = [Item]()
public func documentPicker(_ controller: UIDocumentPickerViewController,didPickDocumentsAt urls: [URL]) {
// Here I am getting user selected file url and its name from iCloud.
// I skipped to paste here.
// User picked file data appending into items array
items.append(Item(url: bookurl, title: name))
// Assign items data to tableData
if let data = UserDefaults.standard.data(forKey:"items") {
do {
let itemsUser = try PropertyListDecoder().decode(Array<Item>.self, from: data)
tableData = itemsUser
} catch { print(error) }
}
}
// MARK - TABLE VIEW DELEGATIONS
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.tableData.count
}
// TableView data-load
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! CustomTableViewCell
let item = tableData[indexPath.row]
cell.name_label.text = item.name
}
return cell
}

Answer 1

For above scenario UserDefault should be outside of the picker delegation. If we maintain within viewDidload with some logic then It will work well.
//Within ViewDidLoad
if let data = UserDefaults.standard.data(forKey:"items") {
do {
let itemsUser = try PropertyListDecoder().decode(Array<Item>.self, from: data)
tableData = itemsUser
} catch { print(error) }
}