Yet another enumeration implementation for Scala for the sake of exhaustive pattern match warnings, Enumeratum is an implementation based on a single Scala macro that searches for implementations of a sealed trait or class.

Enumeratum aims to be similar enough to Scala's built in Enumeration to be easy-to-use and understand while offering more flexibility, safety, and power.

Using Enumeratum allows you to use your own sealed traits/classes without having to maintain your own collection of values, which not only means you get exhaustive pattern match warnings, but also richer enum values, and methods that can take your enum values as arguments without having to worry about erasure (for more info, see this blog post on Scala's Enumeration)

Enumeratum has the following niceties:

• Simplicity; most of the complexity in this lib is in the macro, and the macro is fairly simple conceptually
• No usage of synchronized at runtime , which may help with performance and deadlocks prevention
• No usage of reflection at run time. This may also help with performance but it means Enumeratum is compatible with ScalaJS and other environments where reflection is a best effort.
• All magic happens at compile-time so you know right away when things go awry

Compatible with Scala 2.10.x and 2.11.x

Scaladocs

For basic enumeratum (with no Play support):

libraryDependencies ++= Seq(
    "com.beachape" %% "enumeratum" % "1.3.2"
)

For enumeratum with Play JSON:

libraryDependencies ++= Seq(
    "com.beachape" %% "enumeratum" % "1.3.2",
    "com.beachape" %% "enumeratum-play-json" % "1.3.2"
)

For enumeratum with full Play support:

libraryDependencies ++= Seq(
    "com.beachape" %% "enumeratum" % "1.3.2",
    "com.beachape" %% "enumeratum-play" % "1.3.2"
)

Using Enumeratum is simple. Simply declare your own sealed trait or class A, and implement it as case objects inside an object that extends from Enum[A] as follows.

Note that by default, findValues will return a Seq with the enum members listed in written-order (relevant if you want to use the indexOf method).

import enumeratum._

sealed trait Greeting extends EnumEntry

object Greeting extends Enum[Greeting] {

  val values = findValues

  case object Hello extends Greeting
  case object GoodBye extends Greeting
  case object Hi extends Greeting
  case object Bye extends Greeting

}

// Object Greeting has a `withName(name: String)` method
Greeting.withName("Hello")

// => res0: Greeting = Hello

Greeting.withName("Haro")
// => java.lang.IllegalArgumentException: Haro is not a member of Enum Greeting$@7d6b560b

import Greeting._

def tryMatching(v: Greeting): Unit = v match {
  case Hello => println("Hello")
  case GoodBye => println("GoodBye")
  case Hi => println("Hi")
}

/**
Pattern match warning ...

<console>:24: warning: match may not be exhaustive.
It would fail on the following input: Bye
       def tryMatching(v: Greeting): Unit = v match {

*/

Greeting.indexOf(Bye)
// => res2: Int = 3

The name is taken from the toString method of the particular EnumEntry. This behavior can be changed in two ways. The first is to manually override the def entryName: String method.

import enumeratum._

sealed abstract class State(override def entryName: String) extends EnumEntry

object State extends Enum[State] {

   val values = findValues

   case object Alabama extends State("AL")
   case object Alaska extends State("AK")
   // and so on and so forth.
}

import State._

State.withName("AL")

The second is to mixin the stackable traits provided for common string conversions, Snakecase, Uppercase, and Lowercase.

import enumeratum._
import enumeratum.EnumEntry._

sealed trait Greeting extends EnumEntry with Snakecase

object Greeting extends Enum[Greeting] {

  val values = findValues

  case object Hello extends Greeting
  case object GoodBye extends Greeting
  case object ShoutGoodBye extends Greeting with Uppercase

}

Greeting.withName("hello")
Greeting.withName("good_bye")
Greeting.withName("SHOUT_GOOD_BYE")

The enumeratum-play project is published separately and gives you access to various tools to help you avoid boilerplate in your Play project.

The included PlayEnum trait is probably going to be the most interesting as it includes a bunch of built-in implicits like Json formats, Path bindables, Query string bindables, and form field support.

For example:

package enums._

import enumeratum._

sealed trait Greeting extends EnumEntry

object Greeting extends PlayEnum[Greeting] {

  val values = findValues

  case object Hello extends Greeting
  case object GoodBye extends Greeting
  case object Hi extends Greeting
  case object Bye extends Greeting

}

/*
  Then make sure to import your PlayEnums into your routes in your Build.scala
  or build.sbt so that you can use them in your routes file.

  `routesImport += "enums._"`
*/

The enumeratum-play-json project is published separately and gives you access to Play's auto-generated boilerplate for JSON serialization in your Enum's.

For example:

package enums._

import enumeratum.PlayJsonEnum

sealed trait Greeting

object Greeting extends Enum[Greeting] with PlayJsonEnum[Greeting] {

  val values = findValues

  case object Hello extends Greeting
  case object GoodBye extends Greeting
  case object Hi extends Greeting
  case object Bye extends Greeting

}

The MIT License (MIT)

Copyright (c) 2015 by Lloyd Chan

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.