Match “fallthrough”: executing same piece of code for more than one case?

Question

What is the Scala\'s way to write the following code:

 int i;

 switch(i) {
   case 1:  
         a();
         break;

   case 2:
   case 15:
        b();
          


        

Answer 1

If you are dealing with actual classes (instead of strings or ints), you need _: before each class to make them into a pattern before joining them with |.

sealed trait ShipCondition
case class ShipOnFire() extends ShipCondition
case class FoodSucks() extends ShipCondition
case class MateySnoresTooLoud() extends ShipCondition
case class Ok() extends ShipCondition

val condition = ShipOnFire()

def checkCondition(cond: ShipCondition): Unit = {
  cond match {
    case c @ (_: ShipOnFire | _: FoodSucks) => println("Abandon Ship!") // can also use `c` for something. It has the type ShipCondition
    case (_: MateySnoresTooLoud | _: Ok) => println("Deal with it!")
  }
}

checkCondition(condition) // Abandon Ship!

You get nice exhaustive checking too! Note that you cannot do case class destructuring when using alternative pattern matching (e.g. case (MateySnoresTooLoud(str) | _: Ok) => will fail to compile.