Implementing my domain model in scala using case classes I got

```
abstract class Entity {
    val _id: Option[BSONObjectID]
    val version: Option[BSONLong]
}

```

and several case classes defining the different entities like

```
case class Person (
   _id: Option[BSONObjectID],
   name: String, 
   version: Option[BSONLong]
) extends Entity

```

What I need is a way to set the \_id and version later on from a generic method which operates on an Entity because I have to share this behavior over all Entities and want to avoid writing it down hundreds of times ;-). I would love to be able to

```
def createID(entity: Entity): Entity = {
  entity.copy(_id = ..., version = ...)
}

```

...but of course this does not compile since an Entity has no copy-method. It is generated for each single case class by the compiler...

What is the best way to achieve this in scala?

To prevent somebody asking: I have to use case classes since this is what the third-party-library is extracting for me from the requests I get and the case class instances are what is serialized back to BSON / MongoDB later on...