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Introduction

enumero is a library for concise and safe enumerations in Scala.

import io.buildo.enumero.annotations.enum

@enum trait Planet {
  object Earth
  object Venus
  object Mercury
}

Planet.caseToString(Planet.Earth)
// res0: String = "Earth"

Planet.caseFromString("Earth")
// res1: Option[Planet] = Some(value = Earth)

Motivation

There are a few options for representing enums in Scala.

The built-in scala.Enumeration class has several known issues, which hinder type-safety.

The community tends to shy away from it and prefer an ADT-based encoding such as:

sealed trait Color
object Color {
  case object Red extends Color
  case object Blue extends Color
  case object Green extends Color
}

This approach has many benefits, but it has at least two drawbacks:

  • it's verbose
  • it doesn't provide a way to (de)serialize enum values to (and from) primitive values

enumero tries to tackle these two problems by allowing you to write:

import io.buildo.enumero.annotations.enum

@enum trait Color {
  object Red
  object Blue
  object Green
}

@enum is a macro annotation that automatically translates the code above to the standard ADT-based representation.

@enum also provides some utility functions, to make working with enums easier:

Color.caseToString(Color.Red)
// res3: String = "Red"

Color.caseFromString("Red")
// res4: Option[Color] = Some(value = Red)

Color.values
// res5: Set[Color] = Set(Red, Blue, Green)

Color.name
// res6: String = "Color"
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