如何确定NSManagedObjectID是否为permament？

I want to make sure that an NSManagedObject that I am working with has a permanent NSManagedObjectID. I know that it only is made permanent on [NSManagedObjectContext save:] or [NSManagedObjectContext obtainPermanentIDsForObjects:error:]. However, before I save the context to get a permanent ID, is there a way to determine if an object has a permanent ID or not? That way I don't needlessly save the store.I want to make sure that an NSManagedObject tha