Enumerations

By Andres Jaimes

- 1 minutes read - 197 words

Using case object

Unlike other languages, Scala does not have a keyword for enumerations. One way to implement them is by using case objects. For example:

sealed trait OperatingSystem
case object FreeBsd extends OperatingSystem
case object Debian extends OperatingSystem
case object Alpine extends OperatingSystem
case object Arch extends OperatingSystem
case object Osx extends OperatingSystem

To use it, just define a value of type OperatingSystem. You can even get a string representation from these values:

scala> OperatingSystem.FreeBsd
val res1: OperatingSystem.Value = FreeBsd

scala> OperatingSystem.FreeBsd.toString
val res2: String = FreeBsd

Extending Enumeration

A second option to implement them is to extend from Enumeration:

scala> object OperatingSystem extends Enumeration {
    val FreeBsd, Debian, Alpine, Arch, Osx = Value
}
val res1: object OperatingSystem

scala> OperatingSystem.FreeBsd
val res2: OperatingSystem.Value = FreeBsd

Extending Enumeration is simpler if you have to convert values from strings.

scala> OperatingSystem.FreeBsd.toString
val res3: String = FreeBsd

scala> OperatingSystem.withName("Debian")
val res4: OperatingSystem.Value = Debian

scala> OperatingSystem.withName("Windows")
java.util.NoSuchElementException: No value found for 'Windows'

find can be used to avoid receiving an exception when there’s no certainty about the values you are looking for.

scala> OperatingSystem.values.find(_.toString == "Windows")
val res5: Option[OperatingSystem.Value] = None

References