(Core Data) How to do random sort in NSFetchedResultsController?

Question

Objective-C

My task is to get objects from the database in random order.
First, I generate random ids into an NSArray and pass them as a predicate:

fetchRequest.predicate = [NSPredicate predicateWithFormat:@"(self.id IN %@)", randomIds];
// Пример содержимого массива randomIds (каждый раз разный):
// <__NSArrayM 0xd1cc4e0>(185,51,69,25,33,135,136,97,157,112,145,132,56,15,159,70,88,6,72,82)

However, because the NSFetchedResultsController requires its FetchRequest to be set to sortDescriptors, my results are always sorted:

NSSortDescriptor *sortingDescriptor = [[NSSortDescriptor alloc] initWithKey:@"id" ascending:YES];
fetchRequest.sortDescriptors = @[sortingDescriptor];
fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
                                                                       managedObjectContext:context
                                                                         sectionNameKeyPath:nil
                                                                                  cacheName:nil];

An internet search didn't give me any sane results. How would you solve this problem? Maybe someone has already encountered and came to some kind of solution?

Answer 1

Well, as an option, make a field in Entity, by which you will sort and fill it with random values