Why is my NSFetchedResultsControllerDelegate methods get called randomly when creating a relationship with my entity?

Question

I'm having trouble debugging a NSFetchedResultsControllerDelegate behavior.

My NSFetchedResultsController has a fetch request concerning a Object1 entity. Whenever a cell is touch, I create (and save) a new relationship to a Object2 entity (or use if it exists already).

My problem is that controller:didChangeObject:atIndexPath:forChangeType:newIndexPath: gets called randomly when such a relationship is created (meaning, sometimes it gets called, sometimes it doesn't).

My code creation the relationship is using MagicalRecord :

+ (void)createOrUpdateRelationship:(NSDictionary *)userInfo
                             forObject1:(NSManagedObject1 *)object1 {
    [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {
        NSManagedObject2 *object2 = [NSManagedObject2 fetchObject2ForObject1WithID:object1.ID
                                                                                       inContext:localContext];
        if (!object2) {
            object2 = [NSManagedObject2 MR_createEntityInContext:localContext];
            object2.createdAt = [NSDate date];
        }

        object2.updatedAt = [NSDate date];
        // Store attributes from userInfo

        object2.object1 = [object1 MR_inContext:localContext];
    } completion:^(BOOL contextDidSave, NSError *error) {
        // Celebrate
    }];
}

Any idea what I could do wrong?

Answer 1

Dirty Henry,

Object1 is having a one to one relationship with Object2 and Object2 has inverse relationship with Object1 as well :)

So whenever you change the relationship value of any of these objects other object will also be modified :) Hence NSFetchedResultsController gets triggered :) Thats quite common :)

You cant skip these changes from being triggered.

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
      switch(type) {
             case NSFetchedResultsChangeUpdate:
             //you might consider ignoring it but I wont prefer that though :)
             break;
      }
}