title: Core Data To-Many Relationship Issue
body: <p>I changed my core data model to a to-many relationship.  I believe this is the correct model.  I need to be able to do the following:</p>
  
  <p>(1) A Meal can contain many Foods
  (2) A Food iteme can be linked to many Meals</p>
  
  <p><img src="https://i.stack.imgur.com/oFoRD.png" alt="enter image description here"></p>
  
  <p>I get the following error with when I try to fetch all Foods for a certain Meal.  This worked when it was a one-to-many, but not since I changed it to a to-many relationship.</p>
  
  <pre><code>*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'to-many key not allowed here'
  
  - (NSFetchedResultsController *)fetchedResultsController 
  {       
      self.context = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; 
  
      if (_fetchedResultsController != nil) {
          return _fetchedResultsController;
      }
  
      NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
      NSEntityDescription *entity = [NSEntityDescription entityForName:@"Food" inManagedObjectContext:self.context];
  
      [fetchRequest setEntity:entity];
  
      NSPredicate *foodPredicate = [NSPredicate predicateWithFormat:@"meals == %@", self.meal];
      [fetchRequest setPredicate:foodPredicate];
  
      NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES];
      [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];
      [fetchRequest setFetchBatchSize:20];
  
      NSFetchedResultsController *theFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.context sectionNameKeyPath:nil cacheName:nil];
  
  
      self.fetchedResultsController = theFetchedResultsController;
      _fetchedResultsController.delegate = self;
  
      [fetchRequest release];
      [theFetchedResultsController release];
  
      return _fetchedResultsController;
  }
  </code></pre>