Check out example codes for "view will appear". It will help you in understanding the concepts better.

Code Example 1

override func viewWillAppear(_ animated: Bool) {
        if let context = (UIApplication.shared.delegate as? AppDelegate)?.persistentContainer.viewContext {
            if let coreDataToDoItems = try? context.fetch(ToDoItem.fetchRequest()) as? [ToDoItem] {
                toDo = coreDataToDoItems
                tableView.reloadData()
            }
    }
}

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