How to use switch/case (smiple pattern matching) in Scala?

Question

I've found myself stuck on a very trivial thing :-]

I've got an enum:

object Eny extends Enumeration {
  type Eny = Value
  val FOO, BAR, WOOZLE, DOOZLE = Value
}

In a code I have to convert it conditionally to a number (varianr-number correspondence differs on context). I write:

val en = BAR
val num = en match {
  case FOO => 4
  case BAR => 5
  case WOOZLE => 6
  case DOOZLE => 7
}

And this gives me an "unreachable code" compiler error for every branch but whatewer is the first ("case FOO => 4" in this case). What am I doing wrong?

Answer 1

The following code works fine for me: it produces 6

object Eny extends Enumeration {
  type Eny = Value
  val FOO, BAR, WOOZLE, DOOZLE = Value
}

import Eny._

class EnumTest {
    def doit(en: Eny) = {
        val num = en match {
          case FOO => 4
          case BAR => 5
          case WOOZLE => 6
          case DOOZLE => 7
        }       

        num
    }
}

object EnumTest {
    def main(args: Array[String]) = {
        println("" + new EnumTest().doit(WOOZLE))
    }
}

Could you say how this differs from your problem please?

Answer 2

I suspect the code you are actually using is not FOO, but foo, lowercase, which will cause Scala to just assign the value to foo, instead of comparing the value to it.

In other words:

x match {
  case A => // compare x to A, because of the uppercase
  case b => // assign x to b
  case `b` => // compare x to b, because of the backtick
}