Bizarre issue - "The fetched object at index x has an out of order section name"

Question

I am getting the following error message:

CoreData: error: (NSFetchedResultsController) The fetched object at index 5 has an out of order section name 'James. Objects must be sorted by section name'
Unresolved search error Error Domain=NSCocoaErrorDomain Code=134060 "The operation couldn’t be completed. (Cocoa error 134060.)" UserInfo=0xaa07530 {reason=The fetched object at index 5 has an out of order section name 'James. Objects must be sorted by section name'}, {
    reason = "The fetched object at index 5 has an out of order section name 'James. Objects must be sorted by section name'";
}

I have gone through countless answers on SO which mostly end up pointing to using caseInsensitive compare as the answer however as you can see below my fetch request is already setup to do this:

<NSFetchRequest: 0xc082bd0> (entity: InviteeModel; predicate: (eventId == 148 AND typeOf != "InviteeTypeOfServerContact"); sortDescriptors: ((
    "(lastName, ascending, caseInsensitiveCompare:)",
    "(firstName, ascending, caseInsensitiveCompare:)"
)); batch size: 1000; type: NSManagedObjectResultType; )

I seemed to have narrowed it down to the case where i have two invitees with the same last name (ie. HENRY JAMES and Henry James) then i get the error above saying that James is out of order. If i change both last names to either James or JAMES then it works?!?!?

Here is the code that creates the fetch request:

NSFetchRequest *fetchRequest = [self buildFetchRequest];

// We have to reset the fetched results controller if the sort changes.
// Because otherwise the scrolling index will be inaccurate.
if (self.fetchedResultsController) {
    if (![self.fetchedResultsController.sectionNameKeyPath isEqualToString:self.sortBy]) {
        self.fetchedResultsController = nil;
    }
}


if (!self.fetchedResultsController) {

    NSManagedObjectContext *context = self.event.managedObjectContext;

    NSString *sectionNameKeyPath = nil;
    if (self.sortBy == DefaultSortBy) {

        sectionNameKeyPath = @"sectionChar";
    }
    else {

        sectionNameKeyPath = self.sortBy;
        if ([self.sortBy isEqualToString:@"rsvpState"] || [self.sortBy isEqualToString:@"checkedIn"]) {
            sectionNameKeyPath = @"lastName";
        }
    }

    NSFetchedResultsController *fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
                                                                                               managedObjectContext:context 
                                                                                                 sectionNameKeyPath:sectionNameKeyPath
                                                                                                          cacheName:nil];
    fetchedResultsController.delegate = self;
    self.fetchedResultsController = fetchedResultsController;

and here is a piece from the buildFetchRequest that adds the sortDescriptors:

        NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:self.sortBy
                                                                       ascending:self.shouldSortAscending
                                                                        selector:@selector(caseInsensitiveCompare:)];

        // Add the default sorts (last, first).
        NSSortDescriptor *lastSort = nil;
        NSSortDescriptor *firstSort = nil;
        if (![self.sortBy isEqualToString:@"lastName"]) {
            lastSort = [NSSortDescriptor sortDescriptorWithKey:@"lastName"
                                                     ascending:YES
                                                      selector:@selector(caseInsensitiveCompare:)];
        }
        if (![self.sortBy isEqualToString:@"firstName"]) {
            firstSort = [NSSortDescriptor sortDescriptorWithKey:@"firstName"
                                                      ascending:YES
                                                       selector:@selector(caseInsensitiveCompare:)];
        }

        NSArray *sorts = nil;

        if (lastSort && firstSort) {
            sorts = [[NSArray alloc] initWithObjects:sortDescriptor, lastSort, firstSort, nil];
        }
        else if (lastSort) {
            sorts = [[NSArray alloc] initWithObjects:sortDescriptor, lastSort, nil];
        }
        else {
            sorts = [[NSArray alloc] initWithObjects:sortDescriptor, firstSort, nil];
        }

        [fetchRequest setSortDescriptors:sorts];

Any ideas, this is driving me crazy.

Answer 1

You are setting a fetched results controller section name key path that is different from the first sort descriptor key.

   NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] 
           initWithKey:self.sortBy 
           ascending:self.shouldSortAscending
           selector:@selector(caseInsensitiveCompare:)];

Key is self.sortBy.

if ([self.sortBy isEqualToString:@"rsvpState"] || 
    [self.sortBy isEqualToString:@"checkedIn"]) {
       sectionNameKeyPath = @"lastName";
}

Key is not self.sortBy.

This should result in the error you are seeing.