TableView with two instances of NSFetchedResultsController

Question

After days of research and re-coding I am pretty much stumped. My goal is to get a test app running with a single tableview populated from two separate fetchedResultControllers

Answer 1

The errors you are seeing mean that your UITableView reloads itself before BOTH your NSFetchedResultsControllers do. The codes you posted are probably correct. I suspect that the problem is in one of the NSFetchedResultsControllerDelegate methods.

Answer 2

Well, I think I might have cracked it. As is often the case, stripping it down and reading just a few comments pointed me in the right direction.

When I get to the delegate method controllerDidChangeObject, I attempt to insert a row at the indexPath provided (for the 'checked' item). Except that when inserting into my additional section, this indexPath has no awareness of the fact that there are a bunch of other sections before it. So it receives section 0 and attempts to insert there. Instead, if the indexPath comes from the second FRC, I should be incrementing the section number by the number of sections in the first FRC's table. So, I replaced:

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath { 

UITableView *tableView = self.tableView;

    switch(type) {
        case NSFetchedResultsChangeInsert:
                [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];

        break;

with

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {

UITableView *tableView = self.tableView;

switch(type) {
    case NSFetchedResultsChangeInsert:

        if ([controller.sectionNameKeyPath isEqualToString:@"department"]) {
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
        }
        else {
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:[NSIndexPath indexPathForRow:newIndexPath.row inSection:firstFRC.sections.count]] withRowAnimation:UITableViewRowAnimationFade];         }
        break;

I will need to do this for each of insert, delete, update etc. I will mark this as the answer after I have validated this and to allow time for other comments.