how to sort a view-based tableview

Question

I can't manage to sort a view-based tableview. I use an arrayController that control an entity of core data.

I tried to select a column and in the attribute inspector I used as a sort key the attributes name relative to that column and compare: as a selector... when I build and run I click on the header and now display the arrow that change every click, but the nothing happens with the rows. no sorting.

How can I fix it?
I think I'm missing something easy, but I can't get over it.

Answer 1

You may want to consider using an NSFetchedResultsController. From the Apple documentation for NSFetchedResultsController,

You use a fetched results controller to efficiently manage the results returned from a Core Data fetch request to provide data for a UITableView object.

The code looks like this where the line that provides the sort descriptor starts with NSSortDescriptor.

- (NSFetchedResultsController *)fetchedResultsController
{
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"YourEntityName"
                                              inManagedObjectContext:yourManagedObjectContext];
    [fetchRequest setEntity:entity];

    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"YourSortKey"
                                                                   ascending:YES];

    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
    [fetchRequest setSortDescriptors:sortDescriptors];

    NSError *error = nil;
    NSArray *fetchedObjects = [yourManagedObjectContext executeFetchRequest:fetchRequest 
                                                                      error:&error];
    if (fetchedObjects == nil) {
        // Handle the error
    }

    yourFetchedResultsController = [[NSFetchedResultsController alloc] 
            initWithFetchRequest:fetchRequest 
            managedObjectContext:self.managedObjectContext
              sectionNameKeyPath:nil
                       cacheName:nil];

    return yourFetchedResultsController;
}