Question

I’m stuck at ordering Core Data relationships. I have a to-many relationship but the problem I can’t overcome is that re-ordering relational entities in one view re-orders them in every view they belong to.

Example: People are added to activity1 and are randomly ordered using the moveRowAtIndexPath method. Those same people get added to activity2 and are ordered identically to activity1. How can I stop this?

Relevant code:

 - (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
    NSUInteger fromRow = [fromIndexPath row];
    NSUInteger toRow = [toIndexPath row];

    id object = [[eventAthletes objectAtIndex:fromRow] retain];
    [eventAthletes removeObjectAtIndex:fromRow];
    [eventAthletes insertObject:object atIndex:toRow];

    int i = 0;
    for (object in eventAthletes)
    {
        [object setValue:[NSNumber numberWithInt:i++] forKey:@"athleteDisplayOrder"];
    }

    [self saveContext];

    [object release];
}

I updated the model and made the attribute athleteDisplayOrder transient thinking that by using the key and NOT saving it, I would be able to start fresh in a new event. No Dice.

Answer 1

The identical ordering is expected behavior. If you want to “randomize” the order, you have to explicitly do that by reassigning random athleteDisplayOrderattributes.

EDIT:

If you want to have a special user definable order of athletes for each event one way to solve this is to create a new entity EventAthletes that has to-one relationships both Event and Athlete and also contains a display order attribute.

END EDIT

BTW, you are using an extra data array with core data for display in a table view. Did you know that you can use NSFetchedResultsController to manage your table view datasource much more efficiently?