In Scala, how can a constructor refer to the object it is creating?

Question

I want to implement a prototype-based system in Scala. At the root of the type hierarchy is the ROOT node, which has a prototype that refers to itself.

The following

Answer 1

I don't quite see how you can do this - how can you have a constructed instance of the root node, if you need it to already exist when creating it? So the thing at fault here is your modelling of the problem domain, not Scala (or any other language for that matter)

Surely the root node could have a null prototype, or (more idiomatic scala) an Option prototype?

class Node private[mypackage](val prototype : Option[Node]) {
  private def this() = this(None)
  private def this(ptype : Node) = this(Some(ptype)) //Public c-tor
}

object Node extends (Node => Node) {
  val Root = new Node
  def apply(ptype : Node) = new Node(ptype)
}