Core Data Inverse Relationship Not Being Set

Question

I\'ve got two Entities that I\'ll call A and B. They are configured with To-Many relationships in both directions, so A.myBs and B.myAs are both NSSets.

Here is

Answer 1

I just had the same problem, which was why I saw this question. Maybe my solution will help some people in the same situation.

For me the answer was that in the NSManagedObject subclass I had over-riden:

- (void)willChangeValueForKey:(NSString *)inKey withSetMutation:(NSKeyValueSetMutationKind)inMutationKind usingObjects:(NSSet *)inObjects

- (void)didChangeValueForKey:(NSString *)inKey withSetMutation:(NSKeyValueSetMutationKind)inMutationKind usingObjects:(NSSet *)inObjects

This prevents the correct notifications being sent to the parent class (NSManagedObject) which handles the automatic reverse relationships.

Answer 2

If you're subclassing the Managed Object, shouldn't there be auto-generated to-many relationship methods? So that you would just need to call:

[aObject addBObject:bObject];

Answer 3

I found the error, if you are overriding any of these methods

// KVO change notification
- (void)willChangeValueForKey:(NSString *)key;
- (void)didChangeValueForKey:(NSString *)key;
- (void)willChangeValueForKey:(NSString *)inKey withSetMutation:(NSKeyValueSetMutationKind)inMutationKind usingObjects:(NSSet *)inObjects;
- (void)didChangeValueForKey:(NSString *)inKey withSetMutation:(NSKeyValueSetMutationKind)inMutationKind usingObjects:(NSSet *)inObjects;

it will cause NSManagedObject don't work well and the relationships won't be set correctly

Apple documentation: You must not override these methods.