Question

I am making a view just like the iPhone Calendar ListView. I am using core data and getting appointments and grouping them by date.

However just like in the iPhone listview I need to add a blank section for today even if there are no appointments. I cannot figure out how to do this for a section with no appointments since I am doing the sorting before I create the grouping.

How would I add an empty section to the NSFetchedResultsController and have it resorted so that today’s date is in the correct spot and not at the end of the list?

- (NSFetchedResultsController *)fetchedResultsController {

    /*
     Set up the fetched results controller.
     */
    // Create the fetch request for the entity.
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Appointments" inManagedObjectContext:[[CoreDataHelper sharedInstance] managedObjectContext]];
    [fetchRequest setEntity:entity];
    //[fetchRequest setIncludesPendingChanges:YES];

    // Set the batch size to a suitable number.
    //[fetchRequest setFetchBatchSize:20];

    // Sort using the date / then time property.
    NSSortDescriptor *sortDescriptorDate = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:YES];
    NSSortDescriptor *sortDescriptorTime = [[NSSortDescriptor alloc] initWithKey:@"start_time" ascending:YES selector:@selector(localizedStandardCompare:)];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptorDate, sortDescriptorTime, nil];


    [fetchRequest setSortDescriptors:sortDescriptors];

    // Use the sectionIdentifier property to group into sections.
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:[[CoreDataHelper sharedInstance] managedObjectContext] sectionNameKeyPath:@"date" cacheName:nil];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;
    return fetchedResultsController;
} 

Answer 1

You can’t have empty sections with NSFetchedResultsController – that’s just the way it is designed at the moment, and I would call it a limitation 🙂

This problem has been encountered and addressed by a Timothy Armes who has created a class TAFetchedResultsController, which allows for empty sections. It’s a replacement for NSFetchedResultsController. It also allows you to sort your sections on fields which aren’t the section name (quite handy)

However, you will need to make changes to your Core Data model – it’s not quite a drop in replacement.

https://github.com/timothyarmes/TAFetchedResultsController

But it does work well, and will solve your problem if you are willing to re-do your data model.

Hope this helps 🙂