Core Data: Keypath "objectID" not found in entity
- by Martin Gordon
I'm using NSFetchedResultsController with a predicate to load a list of Documents in my application. I want to load all the Documents except the currently active one.
I am using Rentzsch's MOGenerator to create a _Document class and then I put all my custom code in the Document subclass. _Document generates an objectID property with type DocumentID.
In the class that creates the controller, I set the controller's currentDocID property:
controller.currentDocID = self.document.objectID;
In the controller itself, I lazy load the fetchedResultsController like this:
- (NSFetchedResultsController *)fetchedResultsController {
if (fetchedResultsController != nil) {
return fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Document" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(objectID != %@)", self.currentDocID];
[fetchRequest setPredicate:predicate];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"dateModified" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
[aFetchedResultsController release];
[sortDescriptor release];
[sortDescriptors release];
return fetchedResultsController;
}
When the fetchedResultsController loads, my app crashes with an unhandled exception:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'keypath objectID not found in entity <NSSQLEntity Document id=1>'
It's my understanding that all NSManagedObjects have an objectID, whether temporary or permanent. Is this not the case? Any thoughts?
