How to use Scala enums (Enumeration)

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
}

See also

The Scala Cookbook

If you found this tutorial helpful, you can find over 250 more examples in my book, the Scala Cookbook:

Scala Cookbook

Comments

Permalink

Alvin - /you are the Best ! This is the best explanation I got on Enumeration.
I Love your Scala Cookbook . Also your Blog and posts are simply superb and easy to digest !
Thanks a lot for all your work !

Add new comment

Anonymous format

  • Allowed HTML tags: <em> <strong> <cite> <code> <ul type> <ol start type> <li> <pre>
  • Lines and paragraphs break automatically.