Anything noticably wrong with my code?

Question

Getting some funny bugs here. Is there anything that stands out? Specifically relating to MOC and NSFetchedResultsController. I'm getting some EXC_BAD_ACCESS but not a particular line so its hard to debug.

@implementation RoutineTableViewController

@synthesize routineTableView;
@synthesize entered;
@synthesize managedObjectContext;
@synthesize fetchedResultsController=__fetchedResultsController;

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    if (managedObjectContext == nil) 
    { 
        managedObjectContext = [(CurlAppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; 
    }
    [super viewDidLoad];
}

- (void)viewDidUnload
{
    self.managedObjectContext = nil;
    self.entered = nil;
    self.fetchedResultsController = nil;
    self.routineTableView = nil;
    [super viewDidUnload];
}

- (void)dealloc
{
    [__fetchedResultsController release];
    [managedObjectContext release];
    [routineTableView release];
    [entered release];
    [super dealloc];
}

#pragma mark Add an event

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

    routine.name=entered;

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

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

    NSInteger lastSection = [self.routineTableView numberOfSections] -1;

    [self.routineTableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:[self.routineTableView numberOfRowsInSection:lastSection]-1 inSection:lastSection] atScrollPosition:UITableViewScrollPositionBottom animated:YES];
    [routine release];
    [error release];
}

-(void)showPrompt
{
    AlertPrompt *prompt = [AlertPrompt alloc];
    prompt = [prompt initWithTitle:@"Add Workout Day" message:@"\n \n Please enter title for workout day" delegate:self cancelButtonTitle:@"Cancel" okButtonTitle:@"Add"];
    [prompt show];
    [prompt release];
}

- (void)alertView:(UIAlertView *)alertView willDismissWithButtonIndex:(NSInteger)buttonIndex
{
    if (buttonIndex != [alertView cancelButtonIndex])
    {
        entered = [(AlertPrompt *)alertView enteredText];

       // if(eventsArray && entered)
        {
            [self addRoutine];
        }
    }
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
    return [sectionInfo numberOfObjects];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    //TableViewCell *cell = (TableViewCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    if (cell == nil)
    {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault  reuseIdentifier:CellIdentifier] autorelease];
    }

    Routine *tempRoutine = (Routine *)[__fetchedResultsController objectAtIndexPath:indexPath];
//    [cell setText:tempRoutine.name];
    cell.textLabel.text = tempRoutine.name;
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;    
    return cell;
}


// Override to support conditional editing of the table view.
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the specified item to be editable.
    return YES;
}

-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
 {
     if (editingStyle == UITableViewCellEditingStyleDelete) 
     {
         // Delete the managed object for the given index path
         NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
         [context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];
         NSLog(@"fetched results : \n%@\n",[self.fetchedResultsController fetchedObjects]);

         // Commit the change.
         NSError *error = nil;

         // Update the array and table view.
         if (![managedObjectContext save:&error]) 
         {
             // Handle the error.
         }
         //[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES];
     }
 }

- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath
{
    NSManagedObject *managedObject = [self.fetchedResultsController objectAtIndexPath:indexPath];
    cell.textLabel.text = [[managedObject valueForKey:@"name"] description];
}

#pragma mark - Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Navigation logic may go here. Create and push another view controller.
    [tableView deselectRowAtIndexPath:indexPath animated:YES];

     RoutineDayTableViewController *detailViewController = [[RoutineDayTableViewController alloc] initWithNibName:@"RoutineDayTableViewController" bundle:nil];
    NSManagedObject *managedObject = [self.fetchedResultsController objectAtIndexPath:indexPath];

    detailViewController.title = [[managedObject valueForKey:@"name"] description];
//
//    // Pass the selected object to the new view controller.
//     [self.navigationController pushViewController:detailViewController animated:YES];
//     [detailViewController release];

    detailViewController.theSelectedRoutine = [__fetchedResultsController objectAtIndexPath: indexPath];
    NSLog(@"detailViewController.theSelectedRoutine:%@",detailViewController.theSelectedRoutine);
    [self.navigationController pushViewController:detailViewController animated:YES];
    [detailViewController release];
}

#pragma mark - Fetched results controller

- (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:@"Routine" 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:nil];
    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;
}    

#pragma mark - Fetched results controller delegate


- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
    [self.routineTableView beginUpdates];
}

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
           atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type
{
    switch(type)
    {
        case NSFetchedResultsChangeInsert:
            [self.routineTableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [self.routineTableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
       atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
      newIndexPath:(NSIndexPath *)newIndexPath
{
    UITableView *tableView = self.routineTableView;

    switch(type)
    {

        case NSFetchedResultsChangeInsert:
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeUpdate:
            [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;

        case NSFetchedResultsChangeMove:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
    [self.routineTableView endUpdates];
}
@end

Edit: here is the app delegate.m

@implementation AppDelegate

@synthesize window=_window;
@synthesize rootController;
@synthesize excerciseNavController;
@synthesize managedObjectContext=__managedObjectContext;

@synthesize managedObjectModel=__managedObjectModel;

@synthesize persistentStoreCoordinator=__persistentStoreCoordinator;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    [self.window addSubview:rootController.view];
    [self.window makeKeyAndVisible];
    return YES;
}

- (void)applicationWillResignActive:(UIApplication *)application
{
    /*
     Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
     Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
     */
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    /*
     Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
     If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
     */
}

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    /*
     Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
     */
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    /*
     Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
     */
}

- (void)applicationWillTerminate:(UIApplication *)application
{
    /*
     Called when the application is about to terminate.
     Save data if appropriate.
     See also applicationDidEnterBackground:.
     */
}
- (void)dealloc
{
    [_window release];
    [rootController release];
    [excerciseNavController release];
    [__managedObjectContext release];
    [__managedObjectModel release];
    [__persistentStoreCoordinator release];
    [super dealloc];
}

- (void)saveContext
{
    NSError *error = nil;
    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
    if (managedObjectContext != nil)
    {
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&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();
        } 
    }
}

#pragma mark - Core Data stack

/**
 Returns the managed object context for the application.
 If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
 */
- (NSManagedObjectContext *)managedObjectContext
{
    if (__managedObjectContext != nil)
    {
        return __managedObjectContext;
    }

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil)
    {
        __managedObjectContext = [[NSManagedObjectContext alloc] init];
        [__managedObjectContext setPersistentStoreCoordinator:coordinator];
    }
    return __managedObjectContext;
}

/**
 Returns the managed object model for the application.
 If the model doesn't already exist, it is created from the application's model.
 */
- (NSManagedObjectModel *)managedObjectModel
{
    if (__managedObjectModel != nil)
    {
        return __managedObjectModel;
    }
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Temp" withExtension:@"momd"];
    __managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];    
    return __managedObjectModel;
}


/**
 Returns the persistent store coordinator for the application.
 If the coordinator doesn't already exist, it is created and the application's store added to it.
 */
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    if (__persistentStoreCoordinator != nil)
    {
        return __persistentStoreCoordinator;
    }

    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Temp.sqlite"];

    NSError *error = nil;
    __persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&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.

         Typical reasons for an error here include:
         * The persistent store is not accessible;
         * The schema for the persistent store is incompatible with current managed object model.
         Check the error message to determine what the actual problem was.


         If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.

         If you encounter schema incompatibility errors during development, you can reduce their frequency by:
         * Simply deleting the existing store:
         [[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil]

         * Performing automatic lightweight migration by passing the following dictionary as the options parameter: 
         [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

         Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.

         */
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }    

    return __persistentStoreCoordinator;
}

#pragma mark - Application's Documents directory

/**
 Returns the URL to the application's Documents directory.
 */
- (NSURL *)applicationDocumentsDirectory
{
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}


@end

Answer 1

You really need to use the self.propertyName reference form everywhere in the code except in the accessors for that specific property.

For example: entered is property but everywhere in the code, even when you set the value you use only the direct access form which retains nothing. E.g,

entered = [(AlertPrompt *)alertView enteredText];

Since alertView is almost certainly returning an autoreleased NSString object, that object will disappear without warning the next time the autorelease pool is drained. You will never know from moment to moment whether entered has a value or not.

You really, really, really need to use:

self.entered = [(AlertPrompt *)alertView enteredText];

... to make sure the value is retained.

Answer 2

this bit scares me a bit... you will return a nil MOC, an MOC may never get alloc'd

if (__managedObjectContext != nil)
{
    return __managedObjectContext;
}

NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil)
{
    __managedObjectContext = [[NSManagedObjectContext alloc] init];
    [__managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return __managedObjectContext;

why don't you just do this in your app delegate, do it once.

maybe do something more like:

if (__managedObjectContext != nil)
{
    return __managedObjectContext;
}
__managedObjectContex = [[NSManagedObjectContext alloc] init];


NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil)
{
    //__managedObjectContext = [[NSManagedObjectContext alloc] init];
    [__managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return __managedObjectContext;

Answer 3

I wonder if the managedObjectContext is maybe getting released out from under you because you're not retaining it?

Try this in your viewDidLoad and see if it makes any difference:

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

Answer 4

When you assign your value to managedObjectContext - try doing either of the following:

managedObjectContext = [[(CurlAppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext] retain];

or if your managedObjectContext property has a retain in its definition you can try

self.managedObjectContext = [(CurlAppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; 

Answer 5

If you have an EXEC_BAD_ACCESS you should turn on zombies and rerun your app so you can see what is over released;

http://developer.apple.com/library/ios/#documentation/Xcode/Conceptual/iphone_development/130-Debugging_Applications/debugging_applications.html

Once you know what's over released you will have a much better idea of what is going on.