could not locate an NSManagedObjectModel for entit

Question

This is the code for toggleAddProject method, the Core Data code is almost the same as found in Apple's CoreDataBooks sample, however when I click the add button the app crashes with entityForName: could not locate an NSManagedObjectModel for entity name 'Project' on the line starting with newProjectController.project

-(IBAction)toggleAddProject 
{
    NewProjectViewController *newProjectController = [[[NewProjectViewController alloc] initWithStyle:UITableViewStyleGrouped] autorelease];

    // Create a new managed object context for the new project -- set its persistent store coordinator to the same as that from the fetched results controller's context.
    NSManagedObjectContext *addingContext = [[NSManagedObjectContext alloc] init];
    self.addingManagedObjectContext = addingContext;
    [addingManagedObjectContext setPersistentStoreCoordinator:[[fetchedResultsController managedObjectContext] persistentStoreCoordinator]];
    newProjectController.project = (Project *)[NSEntityDescription insertNewObjectForEntityForName:@"Project" inManagedObjectContext:addingContext];
    [addingContext release];


    UINavigationController *addNewNavigationController = [[UINavigationController alloc] initWithRootViewController:newProjectController];
    [self.navigationController presentModalViewController:addNewNavigationController animated:YES];  
    [addNewNavigationController release];
}

Everything has been synthesized, the Project entity exists. I can't figure out why it crashes. Most people seem to be able to fix this error by inserting the following code either in the method itself, or in viewDidLoad:

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

When modified for my app delegate it makes no difference. Thanks for any help.

Answer 1

During my development, I could not find Entities that I added later on. What worked for me: (Basically a sanity-tip)

Uninstall the App EVERY TIME you change the Data Model!

The Data Model is cached by Core Data between installs, to make sure the integrity stays in tact. Delete the App from the simulator / iPhone to be able to test your changes.

PS: does anyone know how to do that automatically?