在Core Data中向实体添加属性

I've created all of my Managed Objects after mapping out all entities/attributes/relationships in the data model. Now I have the problem of needing to add additional attributes/relationships I haven't thought of when I first designed one of my entities/classes. Is there a way to modify my existing NSManagedObject class with Core Data short of wiping all of my models and re-creating them based on the new xcdatamodel?I've created all of my Managed Objects after ma