iOS Core Data how to properly initialize entity relationships?

问题

I have a one to many relationship in my core data model. I need to create a new entity and save it. The entity has a one to many relationship which generated the following code:

- (void)addRelationshipEvent1:(NSSet *)values;
- (void)removeRelationshipEvent1:(NSSet *)values;

.

        NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
        NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];
        ApplicationRecord *newManagedObject = (ApplicationRecord*)[NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];


        newManagedObject.startDate = [NSDate date];
        newManagedObject.stopDate = [[NSDate date] dateByAddingTimeInterval:120];

//keep adding individual dynamic properties

is it correct to set the -toMany relationship sets to nil initially? Or do I need to initialize an (empty?) set here and assign it? Would I be able to add extra objects later if I set the initial set to nil?

        newManagedObject.relationshipEvent1  = nil;
        newManagedObject.relationshipEvent2 = nil;
    //...

        // Save the context.
        NSError *error = nil;
        if (![context save:&error])
        {
            /*
             Replace this implementation with code to handle the error appropriately.

             abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
             */
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();

        }

回答1:

Alex,

You don't need to intialize your relationships. Just use the supplied accessors or helper functions and Core Data takes care of it. IOW, only worry about the property/relationship when you need to actually use it.

Andrew

来源：https://stackoverflow.com/questions/7920667/ios-core-data-how-to-properly-initialize-entity-relationships