Scala Language Pattern Matching Pattern Matching Sealed Traits
Example
When pattern matching an object whose type is a sealed trait, Scala will check at compile-time that all cases are 'exhaustively matched':
sealed trait Shape
case class Square(height: Int, width: Int) extends Shape
case class Circle(radius: Int) extends Shape
case object Point extends Shape
def matchShape(shape: Shape): String = shape match {
case Square(height, width) => "It's a square"
case Circle(radius) => "It's a circle"
//no case for Point because it would cause a compiler warning.
}
If a new case class for Shape is later added, all match statements on Shape will start to throw a compiler warning. This makes thorough refactoring easier: the compiler will alert the developer to all code that needs to be updated.
