numberOfRowsInSection: for a specific attribute - ios

Question

I have a UITableView that is populated with data from core data and I currently have it set up so that it adjusts the size of the table based on the number of objects in an entity. My problem is that I know have two attributes in this entity. Now the tableview has a bunch of extra cells because it is creating one for everything in the entity, not just creating one per object in a specific attribute. So I would like to set numberOfRowsInSection: based on amount of objects in an attribute, not the whole entity. How would I do this?
How I am currently doing it:
id sectionInfo =
[[_fetchedResultsController sections] objectAtIndex:section];
return [sectionInfo numberOfObjects];
EDIT:
This is what I have tried:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
// id sectionInfo =
// [[_fetchedResultsController sections] objectAtIndex:section];
// return [sectionInfo numberOfObjects];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSManagedObjectContext *context = [self managedObjectContext];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"FeedEntity" inManagedObjectContext:context];
[fetchRequest setEntity:entity];
fetchRequest.predicate = [NSPredicate predicateWithFormat:#"imageData != nill"];
NSFetchedResultsController *theFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:context sectionNameKeyPath:nil cacheName:nil];
id sectionInfo =
[[theFetchedResultsController sections] objectAtIndex:section];
return [sectionInfo numberOfObjects];
}
But this results in this error:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'An instance of NSFetchedResultsController requires a fetch request with sort descriptors'

Answer 1

Ok, well thats an easy solve. Will there always be an image for every single string? Why not just return the yourStringDataArray.length in the -(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section method? This way you will only get the amount of cells needed to display your total amount of strings in your array.

Answer 2

so you have one entity with two attributes. And you need to filter the objects to show for the tableview. I think you need to use NSFetchRequest and NSPredicate to filter your objects by checking the attribute of your object.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSManagedObjectContext *context = [your context];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"FeedEntity" inManagedObjectContext:context];
[fetchRequest setEntity:entity];
fetchRequest.predicate = [NSPredicate predicateWithFormat:#"imageData = nil"];
request.sortDescriptors = [NSArray arrayWithObject:[[NSSortDescriptor alloc] initWithKey:#"text" ascending:NO]];
NSFetchedResultsController *fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:context sectionNameKeyPath:nil cacheName:nil];