CoreData error: +entityForName: could not locate a

问题:

I've been struggling with CoreData for a few days, but I keep getting this error:

'NSInternalInconsistencyException', reason: '+entityForName: could not locate an NSManagedObjectModel for entity name.

I have checked the entity name and what I wrote on my code and they're the same. I also recreated the object data-model and even delete the app from the simulator but nothing seems to fix it. Here's what I have:

method to save into CoreData:

-(IBAction)save:(id)sender {
    NSManagedObject * newNews = [NSEntityDescription insertNewObjectForEntityForName:@"NewsStand"
    inManagedObjectContext:coredata.managedObjectContext];
    [newNews setValue:news_title forKey:@"story_title"];
    [newNews setValue:news_desc forKey:@"story_desc"];
    [newNews setValue:news_image  forKey:@"story_image"];
    [newNews setValue:test  forKey:@"story_url"];
    [coredata commit];
    NSLog(@"data saved!!!!");
}

I have implemented all methods of core data in a separated class:

applicationDocumentsDirectory,  
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator, 
- (NSManagedObjectModel *)managedObjectModel, 
- (NSManagedObjectContext *)managedObjectContext

回答1:

This is a fairly common error and it has three causes:

1. Misspelling the entity name e.g. NewsStand instead of NewsStands.
2. Having a nil managed object context
3. Having no or the wrong managed object model loaded.

(1) is the most common but (3) is more common than (2). You can check that you are loading the right model with the keypath:

aManagedObjectContext.persistentStoreCoordinator.managedObjectModel.entities

then check the entity's names.

回答2:

During my development, I could not find Entities that I added later on. What worked for me:

Uninstall the App EVERY TIME you change the Data Model!

The Data Model is cached by Core Data between installs, to make sure the integrity stays in tact. Delete the App from the simulator / iPhone to be able to test your changes.

PS: does anyone know how to do that automatically?

回答3:

I had a similar problem and found TechZen's answer to be helpful (especially the suggestion to check the entities). However, my problem turned out to be a variant of (2): I could see that the moc itself wasn't nil, but I hadn't set the persistent store coordinator.

[aManagedObjectContext setPersistentStoreCoordinator:persistentStoreCoordinator]

or similar.

I'd add this as a comment to TechZen's answer, but can't yet, and want to include it in case someone else has my problem.

回答4:

Ensure that coredata.managedObjectContext is not nil.

回答5:

Don't have the rep to comment - but Luc Bloom's response fixed MY issue. I completely forgot I changed some stuff in the data model after initial build/install and spent entirely too long banging my head against the desk.

回答6:

If you're editing a framework and running a unit test to get the error, make sure your xcdatamodeld file is added to the test target. Frameworks behave differently than normal projects.