In a subclass of NSManagedObject, "To Many" relationships are generated as an NSSet. However I need the objects in the collection to be in a correct order, is there any potential errors if I replace NSSet with NSArray? Or is there any other ways to achieve that?
Mark your relationship as ordered in the object model designer, and then generate your subclass. It will have an NSOrderedSet as the class of the property for your to-many relationship, which you can use for similar purposes as an NSArray. Get familiar with the differences between the two before you proceed.