NSFetchedResultsController not properly updating tableView - ios

Question

I'm fetching some items (NSManagedObject) in viewDidLoad, and i'm using the NSFetchedResultsController delegates to update tableView cells in swift ios (the delegates from Apple docs for insertion, deletion etc.), the issue is that when I add an item to core data of the same ManagedObject type, i expect the table to update with the new item, but instead the last item is removed from the tableview and the new one isn't added. I only see the new item when I load the screen again... what could be wrong?
Here is my fetchedResultsController:
lazy var fetchedResultsController: NSFetchedResultsController<Message> = {
let context = CoreDataManager.shared.persistentContainer.viewContext
let request: NSFetchRequest<Message> = Message.fetchRequest()
request.sortDescriptors = [
NSSortDescriptor(key: "createdAt", ascending: true)
]
request.fetchLimit = 40
let frc = NSFetchedResultsController(fetchRequest: request, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
// fetch only messages with that recipient id of the chat.
let recipientId = "\(chat!.recipientId)"
request.predicate = NSPredicate(format: "recipientId == %#", recipientId)
return frc
}()
and here is how i'm creating and adding a new message
func createNewTextMessage(recipientId: String, content: String) {
...
guard let id = Int32(recipientId) else { return }
guard let chat = fetchSingleChat(recipientId: id) else { return }
let context = persistentContainer.viewContext
let message = Message(context: context)
let date = Date()
message.chatId = chat.id
message.createdAt = date
message.isRead = false
message.senderId = Int32(currentUserId)
message.senderName = currentUserName
message.senderPhoneNumber = currentUserPhoneNumber
message.status = MessageStatus.unsent.rawValue
message.type = MessageType.text.rawValue
message.owner = MessageOwnerType.mine.rawValue
message.content = content
message.recipientId = chat.recipientId
message.recipientName = chat.title
message.messageId = "\(currentUserToken)_\(date.millisecondsSince1970)"
// here's where i'm setting some relationship (chat to message: 1-to-many)
message.chat = chat
chat.lastMessage = message
message.chat?.lastMessage = message
do {
try context.save()
} catch let err {
print("failed to save private chat:", err)
}
}
The chat ManagedObject has an attribute of lastMessage which is of type Message (also a managed object), i set the newly created message to the Chat's last message. Could the problem be from there.
And here is the delegate code as well:
// MARK: - NSFetchedResultsController Delegates
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
tableView.beginUpdates()
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
switch type {
case .insert:
tableView.insertSections(IndexSet(integer: sectionIndex), with: .fade)
case .delete:
tableView.deleteSections(IndexSet(integer: sectionIndex), with: .fade)
case .move:
break
case .update:
break
}
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
switch type {
case .insert:
tableView.insertRows(at: [newIndexPath!], with: .right)
case .delete:
tableView.deleteRows(at: [indexPath!], with: .fade)
case .update:
tableView.reloadRows(at: [indexPath!], with: .fade)
case .move:
tableView.moveRow(at: indexPath!, to: newIndexPath!)
}
}
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
tableView.endUpdates()
}

Answer 1

Note that your handling of moving rows (.move) only moves one row, you should implement it to move many. Not sure if this solves your problem, it depends on how your data is sorted.
Here is how I have implemented my .move
case .move:
if let indexPath = indexPath {
tableView.removeRows(at: IndexSet(integer: indexPath.item), withAnimation: .effectFade)
}
if let newIndexPath = newIndexPath {
tableView.insertRows(at: IndexSet.init(integer: newIndexPath.item), withAnimation: .effectFade)
}