private classes in scala

private-classes.scala

//
// (1). Use a trait, companion object and private class that
//      implements trait within the companion object
//
sealed trait Point {
  def x: Int
  def y: Int
}

object Point {
  private case class _Point(x: Int, y: Int) extends Point

  // Without an explicit return type, you get the following error:
  //
  // <console>:15: error: private class _Point escapes its defining scope as part of type Point._Point
  //       def apply(x: Int, y: Int) = {
  //
  def apply(x: Int, y: Int): Point = {
    _Point(x, y)
  }
}

scala> Point(1,2)
res0: Point = _Point(1,2)