Sealed classes 

sealed abstract class Furniture
case class Couch() extends Furniture
case class Chair() extends Furniture

def findPlaceToSit(piece: Furniture): String = piece match {
  case a: Couch => "Lie on the couch"
  case b: Chair => "Sit on the chair"
}
sealed abstract class Furniture
case class Couch() extends Furniture
case class Chair() extends Furniture

def findPlaceToSit(piece: Furniture): String = piece match {
  case a: Couch => "Lie on the couch"
  case b: Chair => "Sit on the chair"
}

which means all subtypes must be declared in the same file.

Sealed classes — Structure map

Clickable & Draggable!

Sealed classes — Related pages:

Pattern Matching