Core data: The fetched object at index x has an out of order section name 'xxxxxx. Objects must be sorted by section name

Question

I know I\'m not the first to ask this question but I\'m really stumped..

Basically I have a screen with two buttons. Each button loads data into a tableview below based

Answer 1

I also have got a similar issue, perhaps someone find it useful.

I fetched financial transactions from DB and sectioned them by Month.

DB has property trDate - which is a transaction date. But trMonth is a transient property like:

- (NSString*)trMonth {
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"LLLL"];
[dateFormatter setLocale:[NSLocale currentLocale]];

return [dateFormatter stringFromDate:trDate];
}

It was used in FetchResultsController like this:

...
NSSortDescriptor *sortDate = [[NSSortDescriptor alloc] initWithKey:@"trDate" ascending:YES];

[fetchRequest setSortDescriptors:@[sortDate]];

NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:@"trMonth" cacheName:nil];
...

Which worked well in production, but once app started to crash, and after discovering the root issue I figured out that there two transaction for (for instance) on July: July 2014 and July 2015. That was the crash point as trDate sorted well July 2014 < July 2015, but my method considered them as the same month. The solution was use as section names not only the month name but year also:

- (NSString*)trMonthYear {
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"LLLL yyyy"]; // added year also
[dateFormatter setLocale:[NSLocale currentLocale]];

return [dateFormatter stringFromDate:trDate];
}