Core Data Insertion Error - iphone

Question

I have a to-many relationship with Meals and Food (i.e. Meal <<------>> Food). Food is an abstracted class, and can be either a Fruit or Vegetable. I have a RootViewController that displays all the Food in a given Meal. In one class I add a Vegetable and another I add a Fruit.
I get the following error when I start adding these to a Meal. I am really not sure what is going on and how this is happening.
Assertion failure in -[UITableView _endCellAnimationsWithContext:], /SourceCache/UIKit_Sim/UIKit-1912.3/UITableView.m:1046
CoreData: error: Serious application error. An exception was caught from the delegate of NSFetchedResultsController during a call to -controllerDidChangeContent:. Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (2) must be equal to the number of rows contained in that section before the update (2), plus or minus the number of rows inserted or deleted from that section (1 inserted, 0 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out). with userInfo (null)
2012-03-19 22:52:06.652 iGlucoTouch[682:11903] Meal Name: Meal #1 atIndex: 0
RootViewController.h
#interface RootViewController : UIViewController <UITableViewDelegate, UITableViewDataSource, NSFetchedResultsControllerDelegate>
{
NSFetchedResultsController *_fetchedResultsController;
NSManagedObjectContext *_context;
UITableView *_tableView;
}
#property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController;
#property (nonatomic, retain) NSManagedObjectContext *context;
#property (nonatomic, retain) UITableView *tableView;
#end
RootViewController.m
#implementation RootViewController
#synthesize fetchedResultsController = _fetchedResultsController;
#synthesize context = _context;
#synthesize tableView = _tableView;
- (void)viewDidAppear:(BOOL)animated
{
self.tableView = [[UITableView alloc]initWithFrame:CGRectMake(0, 0, 320, 400) style:UITableViewStyleGrouped];
self.tableView.dataSource = self;
self.tableView.delegate = self;
self.tableView.rowHeight = 60.0;
[self.view addSubview:self.tableView];
[self.tableView release];
NSError *error;
if (![self.fetchedResultsController performFetch:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1);
}
}
- (void)tableView:(UITableView *)tableView
commitEditingStyle:(UITableViewCellEditingStyle)editingStyle
forRowAtIndexPath:(NSIndexPath *)indexPath
{
self.context = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
Food *food = [_fetchedResultsController objectAtIndexPath:indexPath];
if (editingStyle == UITableViewCellEditingStyleDelete) {
[self.meal removeFoodsObject:food];
NSError *error;
if (![self.context save:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1);
}
}
}
- (void)tableView:(UITableView *)tableView
commitEditingStyle:(UITableViewCellEditingStyle)editingStyle
forRowAtIndexPath:(NSIndexPath *)indexPath
{
self.context = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
Food *food = [_fetchedResultsController objectAtIndexPath:indexPath];
if (editingStyle == UITableViewCellEditingStyleDelete) {
[self.meal removeFoodsObject:food];
NSError *error;
if (![self.context save:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1);
}
}
}
- (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:#"ANY 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;
[sort release];
[fetchRequest release];
[theFetchedResultsController release];
return _fetchedResultsController;
}
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller
didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath
forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath
{
switch(type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[self configureCell:[self.tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
break;
case NSFetchedResultsChangeMove:
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller
didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
atIndex:(NSUInteger)sectionIndex
forChangeType:(NSFetchedResultsChangeType)type
{
switch(type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView endUpdates];
}
I add a Fruit or Vegetable like this in another class:
self.context = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
Fruit *fruit = [_fetchedResultsController objectAtIndexPath:indexPath];
[self.meal addFoodsObject:fruit];
NSError *error;
if (![self.context save:&error]) {
NSLog(#"Error: %#", [error localizedDescription]);
}

Answer 1

Apparently I was not setting the fetchedResultsController and the context to nil. I was in the dealloc, but that was not getting called because this was one of the views in a tab bar which was declared at the application delegate. So I simply added the code below. Maybe it is because I am sharing a context.
- (void)viewDidDisappear:(BOOL)animated
{
self.fetchedResultsController = nil;
self.context = nil;
}

Answer 2

Yes - sounds like you didn't add the new entry to the NSArray that the NSFetchResultsController is backed by. Right after you do [self.meal addFoodsObject:fruit] you should also be able to call something like
[self.tableView insertRowsAtIndexPaths: [NSArray arrayWithObject:newIndexPath]
withRowAnimation: UITableViewRowAnimationRight];
yourself. Jeff LaMarche's link is a great explanation.