While working on one of my Scala project, I came across a requirement to create enum values having name and description. I tried to find a solution in Scala for this, while searching this I came across a question, Can I have a Scala enum unlike Java?. Answer to this is both Yes and No.
  • No Because there is no direct approach to create an enum value in Scala having any value other then name.
  • Yes Because we can achieve this by extending Scala enumeration functionality. Another approach could be a Case Objects as Scala pattern matching is quite strong.
Lets discuss about these two approaches

Extending Scala Enumeration

This approach allows us to extend Scala Enumeration functionality, by extending Val class.
Advantages
  • Enumerations will generally be a bit less code to write.
  • Enumerations are a bit easier to understand for someone new to Scala since they are prevalent in other languages.
Extending Scala Enumeration
// Extending Scala Enumeration
abstract class JEnum extends Enumeration {
type value = Value
case class JVal(_name: String, description: Option[String]) extends Val(_name)
protected final def JValue(name: String, description: Option[String]):
Value = JVal(name, description)
implicit def valueToJValue(v: Value): JVal = v.asInstanceOf[JVal]
}
// Using Scala Enumeration
object JCurrency extends JEnum {
val DOLLARS = JValue("Dollars", "USA Currency")
val POUNDS = JValue("Pounds", "UK Currency")
val RUPEES = JValue("Rupees", "Indian Currency")
}
view raw JEnum.scala hosted with ❤ by GitHub

Case Objects

This approach allows us to create Enumeration using Case Objects.
Advantages
  • When using sealed case classes/Case Objects, the Scala compiler can tell if the match is fully specified.
  • Case classes naturally supports more fields than a Value based Enumeration, which supports a name and Id.
Case Objects
sealed trait JCurrency {
def name: String
}
case object DOLLARS extends JCurrency {
val name = "Dollars"
}
case object POUNDS extends JCurrency {
val name = "Pounds"
}
case object RUPEES extends JCurrency {
val name = "Rupees"
}
case class UnknownCurrency(name: String) extends JCurrency
view raw case-objects.scala hosted with ❤ by GitHub