SearchBar of TableView doesn't work - ios

Question

I'm trying to add a SearchBar to a TableView, which is storing its data with CoreData. But when I try to search the TableView isn't updating. I think that the fetch is working, but table is not being updated.
func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
if searchText.isEmpty {
return
}
else {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
let sRequest: NSFetchRequest<Note> = Note.fetchRequest()
sRequest.predicate = NSPredicate(format: "SELF.title CONTAINS[cd] %#", searchText)
sRequest.sortDescriptors = [NSSortDescriptor(key: "date", ascending: true)]
let fetchedResultsController = NSFetchedResultsController(fetchRequest: sRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
print(sRequest)
do {
try fetchedResultsController.performFetch()
} catch {
fatalError("Failed to fetch entities: \(error)")
}
self.mainTable.reloadData()
}
return
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell:UITableViewCell = mainTable.dequeueReusableCell(withIdentifier: "prototypeCell")!
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
let tableRequest: NSFetchRequest<Note> = Note.fetchRequest()
tableRequest.sortDescriptors = [NSSortDescriptor(key: "date", ascending: false)]
var fetchedResultsController = NSFetchedResultsController(fetchRequest: tableRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
do {
try fetchedResultsController.performFetch()
} catch {
fatalError("Failed to fetch entities: \(error)")
}
let noteCell = fetchedResultsController.object(at: indexPath)
cell.textLabel?.text = noteCell.title!
let formatter = DateFormatter()
formatter.dateFormat = "d.M.y, HH:mm"
let dateString = formatter.string(from: noteCell.date! as Date)
cell.detailTextLabel?.text = dateString
return cell
}

Answer 1

The problem is this line:
let fetchedResultsController = NSFetchedResultsController(...
let means that this is a local variable. So you create a new fetched results controller and then throw it away.
Meanwhile, in your cellForRowAt, you refer to something else called fetchedResultsController:
var fetchedResultsController = ...
These are two completely different objects.
The fact is that both are wrong. You should not be doing a fetch every time your table view data source is called upon to consider a row. Look at how the Xcode app templates work! There is one fetched results controller, permanently. It does its fetch once and then just sits there holding the data. That is what you should be doing.