How can I insert new objects at top of UITableView backed by Core Data/NSFetchedResultsController?

Question

I have a tableview that is successfully incorporating an NSFetchedResultsController. However, I need the topmost cell in my tableview to read, "Add new object" and have UITableViewCellEditingStyleInsert instead of the default UITableViewCellEditingStyleDelete.

The FetchResultsController wants to check the managedObjectContext for objects--both to determine number of rows and to populate the table cells. The only way I can think to get around this is to create a dummy object, but I feel like there ought to be a more elegant solution.

UPDATE:

For those who might be curious as to what solution I ended up with, I decided to have my insert cell at the bottom, not the top. Here is the relevant code:

- (void)viewDidLoad {
    [super viewDidLoad];

    // Uncomment the following line to preserve selection between presentations.
    //self.clearsSelectionOnViewWillAppear = NO;

    self.editing = YES;
    self.tableView.allowsSelectionDuringEditing = YES;
    self.tableView.delegate = self;

    RubricAppDelegate *appDelegate = (RubricAppDelegate *)[[UIApplication sharedApplication] delegate];
    managedObjectContext = [appDelegate managedObjectContext];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"myClass" inManagedObjectContext:managedObjectContext];
    NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
    [request setEntity:entity];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"classID" ascending:YES];
    NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
    [request setSortDescriptors:sortDescriptors];
    [sortDescriptor release];

    fetchedResultsController = [[NSFetchedResultsController alloc]
                                               initWithFetchRequest:request 
                                               managedObjectContext:self.managedObjectContext
                                               sectionNameKeyPath:nil cacheName:nil];
    NSError *error;
    [fetchedResultsController performFetch:&error];

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    NSLog(@"Number of sections = %d", [[fetchedResultsController sections] count]);

    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    // Return the number of rows in the section.
    id <NSFetchedResultsSectionInfo> myClass = [[fetchedResultsController sections] objectAtIndex:section];
    NSLog(@"Number of classes = %d", [myClass numberOfObjects]);

    return ([[fetchedResultsController fetchedObjects] count] + 1);

}

// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
    }

    NSLog(@"FRC count + 1 = %d", ([[fetchedResultsController fetchedObjects] count] + 1));

    if (indexPath.row == ([[fetchedResultsController fetchedObjects] count])) {
        cell.textLabel.text = @"Add New Class";
    }
    else {
        myClass *theClass = [fetchedResultsController objectAtIndexPath:indexPath];
        NSLog(@"Class name is: %@", theClass.classTitle);
        cell.textLabel.text = theClass.classTitle;
    }


    return cell;
}

- (UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.row == [[fetchedResultsController fetchedObjects] count]) {
        return UITableViewCellEditingStyleInsert;
    }
    return UITableViewCellEditingStyleDelete;
}

The result (with some junk data):

Now my only issue is getting the delete functions to work properly. You can follow my post on that issue here

Answer 1

Normally the add row is at the bottom.

You can accomplish this by changing the -tableView:numberOfRowsInSection: and the -tableView:cellForRowAtIndexPath: methods to adjust the cell count and adjust for it. So your -tableView:numberOfRowsInSection: would return N+1 and your -tableView:cellForRowAtIndexPath: would get object at N-1 unless N == 0 then it would return your "Add new object" cell.

There is no need to mess with the underlying Core Data elements as this is strictly a UI issue.

Update

But now I'm not sure how to return the count of my fetched objects (assuming that is what I used for "N" in your above answer). Also, wouldn't I want -tableView:cellForRowAtIndexPath to return my "Add new object" cell when the indexPath.row = (N + 1), not N = 0? I may be misunderstanding what "N" equates to, but I thought it just meant count of fetched objects.

Yes it is the count of actual objects.

You do want your -tableView:cellForRowAtIndexPath: to return a cell for your "Add new object" otherwise what is the point? You just want it to return a different type of cell.

All you are doing in this solution is adding a cell that is not part of the NSFetchedResultsController and then compensating for it when you are retrieving an actual object from the NSFetchedResultsController and when the user selects a cell.