NSFetchedResultsController with complicate predicate - ios

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]];