Insert values in relationship field

Question

Im trying to insert values in a core data entity, but when I try to insert in a Relationship field it crash

NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
        NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];
        NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:      [entity name] inManagedObjectContext:context];
        [newManagedObject setValue:[NSDate date] forKey:@"fechaAprovacion"];
        [newManagedObject setValue:[NSDate date] forKey:@"fechaUltimoOficio"];
 //relationship field----->[newManagedObject setValue:[NSNumber numberWithInteger:self.index.row] forKey:@"vObra"]; //<---relationship field

        // Save the context.
        NSError *error = nil;
        if (![context save:&error]) { 
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }

Answer 1

I solve it!! i just have to insert the NSManagedObject that is related some thing like this

NSManagedObject *reporteManagedObject = [NSEntityDescription insertNewObjectForEntityForName:@"Reporte" inManagedObjectContext:self.managedObjectContext];

NSManagedObject *partidaManagedObject = [NSEntityDescription insertNewObjectForEntityForName:@"Avance" inManagedObjectContext:self.managedObjectContext];

[partidaManagedObject setValue:reporteManagedObject forKey:@"avanceReporte"];