Kód k http://blog.v6ak.com/2011/09/dedicnost-u-case-classes.html

classes.scala

package com.v6ak.example.geometry
 
abstract sealed class Shape{
 def color: String
}
 
abstract sealed class Ellipse extends Shape {
 def a: Int
 def b: Int
}
 
private[geometry] final case class GeneralEllipse(color: String, a: Int, b: Int) extends Ellipse{
 override def productPrefix = "Ellipse"
}
 
final case class Circle(color: String, r: Int) extends Ellipse {
 def a=r
 def b=r
}
 
object Ellipse {
 
 def apply(color: String, a: Int, b: Int) = a match {
  case `b` => Circle(color, a)
  case _ => GeneralEllipse(color, a, b)
 }
  
 def unapply(e: Ellipse) = Option(e).map(e => (e.color, e.a, e.b))
 
}

demo.scala

package com.v6ak.example.geometry
 
object Demo extends Application{ // use App instead of Application in Scala <= 2.9
 val a = Circle("yellow", 5)
 val b = Ellipse("yellow", 5, 5)
 val c = Ellipse("yellow", 4, 5)
 println(a + " is equal to " + b + ": " + (a == b) + " (should be true)")
 println(a + " is equal to " + c + ": " + (a == c) + " (should be false)")
}