Question

Look at this example:

class Outer(private val handler: Actor){
  def this() = this(new Handler)  // type Handler not found ? ?

 class Handler extends Actor{
    override  def act() {

    }
  }
}

The compiler complain that class Handler is not found. Is this a bug ?

Answer 1

The inner class Handler has a reference on the outer class instance, and you’re trying to create a new Handler before the outer instance exists — which is impossible.

You can try something like this instead:

class Outer(h: Actor = null) {

  private val handler =
    if (h != null) h
    else new Handler

  class Handler extends Actor {
    override def act() {

    }
  }
}

If you’re worried about using null, you can use the solution described here to replace null in default values for parameters.