Question

I did some changes to my model (but I don’t want migration yet, so I just remove the application, built clean etc.)

However, when I run it on the iPhone or in the simulator, I get the following error:

*** Terminating app due to uncaught exception ‘NSInvalidArgumentException’, reason: ‘executeFetchRequest:error: A fetch request must have an entity.’

I set the entity like this:

NSEntityDescription *entity = [NSEntityDescription entityForName:@"Document" inManagedObjectContext:managedObjectContext];

My managedObjectContext is not nil. But I suspect that it doesn’t load the object model correctly or something similar because If I display the entities in the model, the list is empty:

managedObjectModel = [[NSManagedObjectModel mergedModelFromBundles:nil] retain];
NSLog(@"%d", [[managedObjectModel entities] count]);

How can I make sure the model is loaded?

Answer 1

Where are you “displaying the entities”? If they don’t show up in the data model editor, they aren’t there.

You can use -[NSManagedObjectModel entities] to get an array of the entities that the model has.

In turn, you can use -[NSPersistentStore managedObjectModel] to see what model is loaded and then query its entities.

Gotta tell you however, most of the time this error is caused by a spelling typo. That’s why its good to use defines or class methods to return entity names.