Help with NSFetchedResultsController

Question

Please help with this issue of using NSFetchedResultsController.

I created an object of NSFetchedResultsController and I use it once in the method: tableView:cellForRowAtIndexPath: and when I try to execute the same code in the method tableView:didSelectRowAtIndexPath: I get EXC_BAD_ACCESS.

Here is the code of the 2 methods

- (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];
    }

    Person *person = [fetchedResultsController objectAtIndexPath:indexPath];
    cell.textLabel.text = person.name; //This works fine

    [person release];

    return cell;
}

and here is the problematic snippet:

 - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    PhotoListViewController *photoListViewController = [[PhotoListViewController alloc] initWithNibName:@"PhotoListViewController" bundle:nil];

    //The next line returns a bad object or undefined memory
    Person *person = [fetchedResultsController objectAtIndexPath:indexPath];
    //causing the call of [person name] to return EXC_BAD_ACCESS
    photoListViewController.person = [person name];
    [self.navigationController pushViewController:photoListViewController animated:YES];

    [photoListViewController release];
    [person release];
}

Please help me understand why the code is breaking there. Appreciate any suggestions.

Answer 1

Person *person = [fetchedResultsController objectAtIndexPath:indexPath]; 
cell.textLabel.text = person.name; //This works fine
[person release];

[person release] is the problem - no need to release person if it's not alloc'd there. That causes person to be over-released, leading to the crash when something else tries to access it.

Answer 2

Even though, in this example, it's ok to manipulate an autoreleased object (due to simplicity of the manipulations, i.e. you are just grabbing one property of *person), the proper way would be to retain your Person object and release it at the end:

Person *person = [[fetchedResultsController objectAtIndexPath:indexPath] retain];
// bla bla
[person release];