Invalid update: invalid number of rows in section

Question

I am working on a project using Microsoft Azure services. In that while deleting a row I am getting this error:

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 (2) must be equal to the number of rows 
contained in that section before the update (2), plus or minus the number of rows inserted or deleted from that section (0 inserted, 1 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).

Code for table load and delete row is as :

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
        return 3;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    //medicine list
    if (section == 0) {
        NSArray *sectionInfo = [self.fetchedResultsController1 fetchedObjects];
        return [sectionInfo count];

    }
    //allergy list
    else if (section == 1) {
        NSArray *sectionInfo = [self.fetchedResultsController2 fetchedObjects];
        return [sectionInfo count];

    }
    //notes list
    else if (section == 2){
        NSArray *sectionInfo = [self.fetchedResultsController3 fetchedObjects];
        return [sectionInfo count];
    }
    else
        return 0;
 }

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *cellIdentifier = @"mcell";
    MedicationTableViewCell *cell = (MedicationTableViewCell *)    [tableView dequeueReusableCellWithIdentifier:cellIdentifier forIndexPath:indexPath];

    //  Add utility buttons 
    NSMutableArray *rightUtilityButtons = [NSMutableArray new];
    [rightUtilityButtons sw_addUtilityButtonWithColor: [UIColor colorWithRed:1.0f green:0.231f blue:0.188 alpha:1.0f] title:@"Delete"];

    switch (indexPath.section) {
        case 0: {
            NSManagedObject *item = [self.fetchedResultsController1 objectAtIndexPath:indexPath];
            cell.textLabel.text = [item valueForKey:@"name"];
            break;
        }
        case 1: {
            NSManagedObject *item = [self.fetchedResultsController2 objectAtIndexPath:[NSIndexPath indexPathForRow:indexPath.row inSection:0]];
            cell.textLabel.text = [item valueForKey:@"name"];
            break;
        }
        case 2: {
            NSManagedObject *item = [self.fetchedResultsController3 objectAtIndexPath: [NSIndexPath indexPathForRow:indexPath.row inSection:0]];
            cell.textLabel.text = [item valueForKey:@"title"];
            break;
        }
        default:
            break;
    }
    cell.rightUtilityButtons = rightUtilityButtons;
    cell.delegate = self;

    return cell;
}

- (void)swipeableTableViewCell:(SWTableViewCell *)cell didTriggerRightUtilityButtonWithIndex:(NSInteger)index {

 // Delete button is pressed
 NSIndexPath *cellIndexPath = [self.medicationsTableView indexPathForCell:cell];

 //fetchingg data from local store first
 NSManagedObject *item = [self.fetchedResultsController1 objectAtIndexPath:[NSIndexPath indexPathForRow:cellIndexPath.row inSection:0]];

   NSMutableArray *keys = [[NSMutableArray alloc] initWithObjects:@"id", @"name", @"userId", nil];
   NSMutableArray *values = [[NSMutableArray alloc] initWithObjects: [item valueForKey:@"id"], [item valueForKey:@"name"], [item valueForKey:@"userId"], nil];

    //creating dictionary of data
    NSDictionary *dict = [[NSDictionary alloc] initWithObjects:values forKeys:keys];

    //calling delete fucntion
    [self.authService deleteItem:self.syncTable withDict:dict completion:^{
    //removing row from table view
    [self.medicationsTableView reloadData];
    [self.medicationsTableView deleteRowsAtIndexPaths:@[cellIndexPath] withRowAnimation:UITableViewRowAnimationRight];
      }];
      break;
}

Please tell where I am going wrong. Thanks in advcance!!!!

Answer 1

In - (void)swipeableTableViewCell: didTriggerRightUtilityButtonWithIndex:

You need to remove either

[self.medicationsTableView reloadData]; 

or

[self.medicationsTableView deleteRowsAtIndexPaths:@[cellIndexPath] withRowAnimation:UITableViewRowAnimationRight];

Because on first line when reloadData get called it's reload the tableview with new datasource and again calling deleteRowsAtIndexPaths tried to delete a rows which already removed by calling reloadData earlier.

Answer 2

The important thing is that you need to use either

[self.medicationsTableView reloadData];

or

[self.medicationsTableView deleteRowsAtIndexPaths:@[cellIndexPath] withRowAnimation:UITableViewRowAnimationRight];

The reason being, when the tableview's reload data is called the row which is removed from data source is deleted and after that when the delete row api is called for the same index path(where the row is already deleted causes the issue)

Also just before deleting the row from the table delete the object from the data source (self.fetchedResultsController1) and call

[self.medicationsTableView deleteRowsAtIndexPaths:@[cellIndexPath] withRowAnimation:UITableViewRowAnimationRight];

and after the above row's deletion animation is completed than you can call(but it is not required)

[self.medicationsTableView reloadData];