How to use Scala enums (Enumeration)

By Alvin Alexander. Last updated: December 17, 2017

Problem: In Scala, you want to use something that works like a Java enum.

Solution

Extend the scala.Enumeration class to create your Scala enumeration:

package com.acme.app {

    object Margin extends Enumeration {
        type Margin = Value
        val TOP, BOTTOM, LEFT, RIGHT = Value
    }

}

Then import the enumeration to use it in your application:

object Main extends App {

    import com.acme.app.Margin._

    // use an enumeration value in a test
    var currentMargin = TOP
    
    // later in the code ...
    if (currentMargin == TOP) println("working on Top")

    // print all the enumeration values
    import com.acme.app.Margin
    Margin.values foreach println

}

Enumerations are useful tool for creating groups of constants, such as days of the week, months of the year, and many other situations where you have a group of related, constant values.

Using Scala traits as enums

You can also use the following approach of using a Scala trait to create the equivalent of a Java enum. Because it uses a “case object” approach it generates about four times as much code as an Enumeration, but depending on your needs it can also be a good approach:

// a "heavier" approach
package com.acme.app {
    sealed trait Margin
    case object TOP extends Margin
    case object RIGHT extends Margin
    case object BOTTOM extends Margin
    case object LEFT extends Margin
}