Question

I have a simple CoreData app which allows you to add items to a list, displayed in a table view. When the user types in a new item, the following method is called:

- (void)addNewItem:(NSString *)item
{
    // Create a new instance of the entity managed by the fetched results controller.
    NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
    NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];
    Item *newItem = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];

    [newItem setName:item];

    // Save the context.
    NSError *error = nil;
    if (![context save:&error])
    {
        //error handling code
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    [context release];
    [entity release];
    [newItem release];

The app always allows you to add one item to the list, but then crashes if you try to add a second. If I remove “[newItem release];”, the app will allow you to add 4 list items, and then suddenly crash when you try to enter a fifth.

The app will only work properly if all three of those release statements at the end of the method are removed. Can anyone explain why?

Answer 1

The objects are all autoreleased (because you never alloc init anything), so you’re not supposed to release them yourself. It’s not predictable when your app will crash as far as I can tell, but it will eventually crash.