Question

When I try to build my Core Data App, which most code is coming from CoreDataBooks example, I get the error

'+entityForName: could not locate an NSManagedObjectModel for entity name 'Child''

So, after reading, I found the possible causes(See This Older Stack Overflow Question):

• Nil managed object context object.
• Failure to add the model containing the entity to the persistent store the context uses.
• Failure to add the correct persistent store to the context itself.

My question is, how can I tell which of these causes the error, and how can I fix it. I have little experience in debugging and core data, so this is all new.

Answer 1

Most likely, it is the managedObjectContext coming up nil. The way I go about solving this is either to pass the managedObjectContext to the view controller in question from the previous (if it is navigation-based) or to declare the context explicitly in the viewDidLoad like follows:

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

This will get the context created in your app delegate file and apply it to the view in which you are using it. There are many ways to go about assigning the context, but this is probably the most direct