NSFetchedResultsController with complicate predicate

Question

I'm developing the app with UICollectionView.
It's collection of events arranged by date. I'm using NSFetchedResultsController to fetch data from DB. But I need to fetch current and future events + 2 past events. For NSFetchRequest I'm using NSCompoundPredicate

NSPredicate *nextPredicate = [NSPredicate predicateWithFormat: @"startAt >= %@", [NSDate date]];
NSPredicate *previousPredicate = [NSPredicate predicateWithFormat:@"startAt < %@", [NSDate date]];
NSCompoundPredicate *resultPredicate = [NSCompoundPredicate andPredicateWithSubpredicates: @[nextPredicate, previuosPredicate]];
fetchRequest.predicate = resultPredicate;

And I have no idea how to limit previousPredicate to receive only 2 items.

Answer 1

If you know the date of current event than create a method that return date of the last event to fetch and then set the predicate on the main NSFetchRequest to that date.

 -(NSDate *)dateOfPastEvent{
    NSFetchRequest *request = [[NSFetchRequest alloc]init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"EntityName" inManagedObjectContext:_mainContext];
    [request setEntity:entity];

    NSSortDescriptor *sortDesc = [NSSortDescriptor sortDescriptorWithKey:@"startAt" ascending:NO];
    [request setSortDescriptors:@[sortDesc]];

    NSError *error = nil;
    NSArray *array = [_mainContext executeFetchRequest:request error:&error];


    __block NSDate *pastEventDate;

    [array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop){

        if ([obj valueForKey:@"startAt"] == currentEventDate) {
            if (array.count >= idx+2) {
                pastEventDate = [[array objectAtIndex:idx+2] valueForKey:@"startAt"];
                *stop = YES;
            }

        }
    }];


    return pastEventDate;

}

Now set the predicate for the above returned date

  NSFetchRequest *requestForController = [[NSFetchRequest alloc]init];
  NSEntityDescription *entity = [NSEntityDescription entityForName:@"EntityName" inManagedObjectContext:_mainContext];
    [requestForController setEntity:entity];

  NSPredicate *predicate = [NSPredicate predicateWithFormat: @"startAt >= %@", [self dateOfPastEvent]];