NSFetchedResultsController custom sort not getting called

Question

I am currently trying to populate a UITableView in my project from Core Data using NSFetchedResultsController. I am using a custom search with a comparator (although I have

Answer 1

There are a couple of things I can think of. First, though this may not be your problem, you cannot sort on transient properties. But more likely is that when sorting in a model backed by a SQL store, the comparator gets "compiled" to a SQL query, and not all Objective-C functions are available. In this case, you'd need to sort in memory after the fetch is performed.

EDIT: See this doc, specifically the Fetch Predicates and Sort Descriptors section.

Answer 2

I see the same problem and a way to work around it is to modify an object, save the change then restore it to its original value and save again.

    // try to force an update for correct initial sorting bug
NSInteger count = [self.fetchedResultsController.sections count];
if (count > 0) {
    id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:0];
    count = [sectionInfo numberOfObjects];
    if (count > 0) {
        NSManagedObject *obj = [self.fetchedResultsController objectAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]];
        NSString *name = [obj valueForKey:@"name"];
        [obj setValue:@"X" forKey:@"name"];
        // Save the context.
        [self saveContext];
        [obj setValue:name forKey:@"name"];
        // Save the context.
        [self saveContext];
    }
}

Answer 3

Sorry, but did you miss the final fetch part to your code snippet?:

NSError *error;
BOOL success = [aFetchedResultsController performFetch:&error];

Don't forget to release the request too:

[fetchRequest release];