Question

I may just be passing data between views completely wrong here, so I am open to completely changing how I pass my data back and forth.

My app delegate creates the NSManagedObjectContext and passes that to my main menu using a UINavigationController which makes it the root view:

MainMenuViewController *mainMenuViewController = [[MainMenuViewController alloc] init];

NSManagedObjectContext *context = [self managedObjectContext];
if (!context) {
    // Handle the error.
}
// Pass the managed object context to the view controller.
mainMenuViewController.managedObjectContext = context;

UINavigationController *aNavigationController = [[UINavigationController alloc] initWithRootViewController:mainMenuViewController];
self.theNavController = aNavigationController;

[[self theNavController] setNavigationBarHidden:YES animated:NO];

[window addSubview:theNavController.view];
[window makeKeyAndVisible];

[mainMenuViewController release];
[aNavigationController release];

Then when they select a different view controller from the main menu, I initialize the new view controller, pass the NSManagedObjectContext to it, then push it onto the UINavigationController:

BombsViewController *bombsViewController = [[BombsViewController alloc] init];
bombsViewController.managedObjectContext = self.managedObjectContext;
[self.navigationController pushViewController:bombsViewController animated:YES];
[bombsViewController release];

All is fine until I decide to go back to the main menu from my BombsViewController. I am attempting to use the following to pop the root view controller back onto the UINavigationController:

[self.navigationController popToRootViewControllerAnimated:YES];

However, I can’t see a way to send the root view controller my NSManagedObjectContext back since the popToRootViewControllerAnimated method doesn’t accept a view. I tried using the popToViewController:animated: method but then the app crashes with a “terminate called after throwing an instance of ‘NSException’“, “Program received signal: “SIGABRT”.“:

MainMenuViewController *mainMenuViewController = [[MainMenuViewController alloc] init];
mainMenuViewController.managedObjectContext = self.managedObjectContext;
[self.navigationController popToViewController:mainMenuViewController animated:YES];
[mainMenuViewController release];

Answer 1

Why would you send it back? Your root view controller has not been -dealloc‘ed so it still exists in memory and still has a reference to the NSManagedObjectContext. There is nothing to pass back.

The error you are getting is not Core Data related. Run it in the debugger and set a breakpoint on objc_exception_throw and see where it is crashing.