NSFetchedResultsController getting crash while displaying in Tableview - ios

Question

I am getting server response as like below
[[“image_url": https://someurl1, "title": Title1], ["image_url": https://someurl2, "title": Title2], ["image_url": https://someurl3, "title": Title3], ["image_url": https://someurl4, "title": Title4]]
I am storing this data to core data by loop.
So, I am trying to fetch this data from core data using NSFetchedResultsController and I am trying to display in Tableview
func saveDataToDataBase(json: [[String: Any]]) {
for eachData in json {
Categories.saveCategories(jsonResponse: eachData, completionHandler: { [weak self] success in
if (success) {
}
})
}
DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
self.fetchData()
}
}
func fetchData() {
fetchedResultsController = NSFetchedResultsController(fetchRequest: allCategoriesData(), managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
fetchedResultsController?.delegate = self
do {
try fetcheResultsController()!.performFetch()
} catch let error as NSError {
print("Could not fetch. \(error), \(error.localizedDescription)")
}
}
func allCategoriesData() -> NSFetchRequest<NSFetchRequestResult> {
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: HomeKeyConstant.Entity_Categories)
let sortDescriptor = NSSortDescriptor(key: HomeKeyConstant.categories_Id, ascending: true)
fetchRequest.predicate = nil
fetchRequest.sortDescriptors = [sortDescriptor]
return fetchRequest
}
// UITableviewDelegate & Data Source methods
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
guard let sectionCount = fetchedResultsController.sections?.count else {
return 0
}
return sectionCount
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if self.fetchedResultsController == nil {
} else {
if let sectionData = fetchedResultsController.sections?[section] {
return sectionData.numberOfObjects
}
}
return 0
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = homeTableView.dequeueReusableCell(withIdentifier: HomeKeyConstant.key_Cell_Identifier, for: indexPath) as! HomeTableViewCell
self.configureCell(cell, at: indexPath)
return cell
}
func configureCell(_ cell: HomeTableViewCell?, at indexPath: IndexPath?) {
let category = fetchedResultsController.object(at: indexPath!) as! Categories
cell?.tableTitleLabel.text = category.value(forKey: HomeKeyConstant.categories_Title) as? String
cell?.tableDescriptionLabel.text = category.value(forKey: HomeKeyConstant.ctegories_Description) as? String
}
// MARK: - FetchedResultsController Delegate
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
homeTableView.beginUpdates()
}
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
homeTableView.endUpdates()
}
func controller(controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {
switch type {
case .insert:
homeTableView.insertSections(NSIndexSet(index: sectionIndex) as IndexSet, with: .automatic)
case .delete:
homeTableView.deleteSections(NSIndexSet(index: sectionIndex) as IndexSet, with: .automatic)
default: break
}
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
switch type {
case .insert:
homeTableView.insertRows(at: [(newIndexPath! as IndexPath)], with: .automatic)
case .delete:
homeTableView.deleteRows(at: [(indexPath! as IndexPath)], with: .automatic)
default: break
}
}
Actually, I am storing 4 indexes of data. While fetching its showing as 50 indexes and crashig
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (50) must be equal to the number of rows contained in that section before the update (0), plus or minus the number of rows inserted or deleted from that section (1 inserted, 0 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).'
I have a doubt, In my tableview I dont have edit/delete/insert/update options. Just I have to fetch data from database and I have to show in tableview.
So, these NSFetchedResultsControllerDelegate methods are required to implement or not required?
How to fix this crash?

Answer 1

I think the problem here is you you save data to your database. When you saved, you don't wait for them to finish and update your TableviewController. So if you have a little data to save. This code will work otherwise, it's will be crashed.