Question

I just can’t seem to get this working its been weeks I’ve been trying.

It seems like I fix one, thing, and something else crashes, its like a back and forth process with no end.

This table shows objects of entity “Exercise” for each object “Routine”.

My data model:

I’m just posting my full code if anyone sees anything that may be causing problems.

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.routineTableView.delegate = self;
    UIBarButtonItem *addButton = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(exerciseChooser)];
    self.navigationItem.rightBarButtonItem = addButton;
    [addButton release];

    if (managedObjectContext == nil) 
    { 
        managedObjectContext = [(CurlAppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; 
        [managedObjectContext retain];
    }
    [self loadData];
}

-(void)loadData
{
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Exercise" inManagedObjectContext:managedObjectContext];
    [request setEntity:entity];

    NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];

    NSManagedObject *selectedObject = [entityArray objectAtIndex:indexPath.row];

    //Set Predicate

    NSLog(@"After managedObjectContext: %@",  managedObjectContext);

    NSError *error = nil;
    NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
    if (mutableFetchResults == nil) {
        // Handle the error.
    }
    self.entityArray = mutableFetchResults;

    [request setPredicate: [NSPredicate predicateWithFormat: @"routineExercises = %@", selectedObject]];    

    [mutableFetchResults release];
    [request release];

}
-(void)addExercise
{   
    UIBarButtonItem *addButton = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(exerciseChooser)];
    self.navigationItem.rightBarButtonItem = addButton;
    [addButton release];

    if (managedObjectContext == nil) 
    { 
        managedObjectContext = [(CurlAppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; 
        [managedObjectContext retain];
    }

    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Exercise" inManagedObjectContext:managedObjectContext];
    [request setEntity:entity];

    NSError *error = nil;
    NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
    if (mutableFetchResults == nil) {
        // Handle the error.
    }

    Exercise *exercise = (Exercise *)[NSEntityDescription insertNewObjectForEntityForName:@"Exercise" inManagedObjectContext:managedObjectContext];

    exercise.name = selectedExercise;

    NSMutableSet *exercises = [NSSet setWithObjects:exercise,nil];

    Routine *routine = (Routine *)[NSEntityDescription insertNewObjectForEntityForName:@"Routine" inManagedObjectContext:managedObjectContext];

    routine.routineExercises = exercises;    

    if (![managedObjectContext save:&error]) 
    {
        // Handle the error.
    }
    NSLog(@"%@", error);

    [self.routineTableView reloadData];
    [mutableFetchResults release];
    [request release];
}

- (NSFetchedResultsController *)fetchedResultsController
{
    if (fetchedResultsController != nil)
    {
        return fetchedResultsController;
    }

    // Create the fetch request for the entity.
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Exercise" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];

    // Set the batch size to a suitable number.
    [fetchRequest setFetchBatchSize:20];

    // Edit the sort key as appropriate.
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:NO];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];

    [fetchRequest setSortDescriptors:sortDescriptors];

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    [aFetchedResultsController release];
    [fetchRequest release];
    [sortDescriptor release];
    [sortDescriptors release];

    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&error])
    {
        /*
         Replace this implementation with code to handle the error appropriately.

         abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
         */
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return fetchedResultsController;
}   

Update: updated addExercise method (still not working though, its crashing)

-(void)addExercise
{   
    UIBarButtonItem *addButton = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(exerciseChooser)];
    self.navigationItem.rightBarButtonItem = addButton;
    [addButton release];

    NSError *error = nil;

    Exercise *exercise = (Exercise *)[NSEntityDescription insertNewObjectForEntityForName:@"Exercise" inManagedObjectContext:managedObjectContext];

    exercise.name = selectedExercise;

    [theSelectedRoutine addRoutineExercisesObject: exercise];

    if (![managedObjectContext save:&error]) 
    {
        // Handle the error.
    }
    NSLog(@"%@", error);

    [self.routineTableView reloadData];

}

Answer 1

What that error message means is that you tried to access a property called routine in your Exercise class, but according to your diagram, there’s no such thing!

You should rename routineExercises in your Excercise class to routine and set it as the inverse relationship for the routineExercises in the Routine class.