ios core data to AZ indexed tableview - ios

Question

I'm trying to show the values of my core data model to an A-Z indexed table based on the first letter on my attributes (similar to the iOS address book app). The "Favorites" entity of my core data model has 2 attributes: username and status. I want to display only the usernames with status = accepted to the A-Z indexed table.
Here is my code:
- (NSFetchedResultsController *)fetchedResultsController {
if (fetchedResultsController != nil) {
return fetchedResultsController;
}
NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Favorites" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
NSString *status = #"accepted";
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"status == %#",status];
[fetchRequest setPredicate:predicate];
// Create the sort descriptors array.
NSSortDescriptor *usernameDescriptor = [[NSSortDescriptor alloc] initWithKey:#"username" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:usernameDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
// Create and initialize the fetch results controller.
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:#"username" cacheName:#"Root"];
self.fetchedResultsController = aFetchedResultsController;
fetchedResultsController.delegate = self;
return fetchedResultsController;
}
Now when I'm trying to access the section name I get (null)
-(NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
NSLog(#"%#",[[[fetchedResultsController sections] objectAtIndex:section] name]);
return [[[fetchedResultsController sections] objectAtIndex:section] name];
}
Also I thing that with that way I will get the the name and not the first char in order to display it as a section title.

Answer 1

You need to access the sectionsInfo object properly:
id <NSFetchedResultsSectionInfo> info =
[fetchedResultsController sections][section];
return [info name];
However, this will give you a heading for each unique name, probably not want you want. Instead, you have to give your entity a transient property e.g. NSString *sectionIdentifier and write a getter for it that returns the first letter of the username attribute.
If want an index from A-Z running down on the right edge of the table view you additionally have to implement:
sectionIndexTitlesForTableView: and
tableView:sectionForSectionIndexTitle:atIndex:.
If you still get null for your titles, maybe they are not set or persisted in your entity? Maybe you got zero results? Maybe your fetchedResultsController is nil? There are a number of flaws in your data model, so this seems quite possible.
Your entity name Favorites is plural. That is not logical, you should name it Favorite as one instance only describes one favourite.
The status is a string which is also very inefficient. Instead, you should use a number and apply some enum scheme.
The username is a property of Favorite. That seems also very messy because presumably, you also have a User entity which has a username attribute. You should use a relationship to model this.

Answer 2

use NSFetchedResultsController's sectionIndexTitles function to get array of first char