Enumeratum

Enumeratum is a type-safe and powerful enumeration implementation for Scala that offers exhaustive pattern match warnings, integrations with popular Scala libraries, and idiomatic usage that won't break your IDE. It aims to be similar enough to Scala's built in Enumeration to be easy-to-use and understand while offering more flexibility, type-safety (see this blog post describing erasure on Scala's Enumeration), and richer enum values without having to maintain your own collection of values.

Enumeratum has the following niceties:

Zero dependencies
Performant: Faster thanEnumeration in the standard library (see benchmarks)
Allows your Enum members to be full-fledged normal objects with methods, values, inheritance, etc.
ValueEnums that map to various primitive values and have compile-time uniqueness constraints.
Idiomatic: you're very clearly still writing Scala, and no funny colours in your IDE means less cognitive overhead for your team
Simplicity; most of the complexity in this lib is in its macro, and the macro is fairly simple conceptually
No usage of reflection at runtime. This may also help with performance but it means Enumeratum is compatible with ScalaJS and other environments where reflection is a best effort (such as Android)
No usage of synchronized, which may help with performance and deadlocks prevention
All magic happens at compile-time so you know right away when things go awry
Comprehensive automated testing to make sure everything is in tip-top shape

Enumeratum is published for Scala 2.10.x, 2.11.x, and 2.12.x as well as ScalaJS.

Integrations are available for:

Play: JVM only
Play JSON: JVM only (included in Play integration but also available separately)
Circe: JVM and ScalaJS
UPickle: JVM and ScalaJS
ReactiveMongo BSON: JVM only
Argonaut: JVM only

Quick start
SBT
Usage
More examples
Enum 1. Mixins
ValueEnum
ScalaJS
Play integration
Play JSON integration
Circe integration
UPickle integration
ReactiveMongo BSON integration
Argonaut integration
Slick integration
Benchmarking
Publishing

Quick start

SBT

In build.sbt, set the Enumeratum version in a variable (for the latest version, set val enumeratumVersion = the version you see in the Maven badge above).

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

Enumeratum has different integrations that can be added to your build à la carte. For more info, see the respective sections in the Table of Contents

Usage

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

import enumeratum._

sealed trait Greeting extends EnumEntry

object Greeting extends Enum[Greeting] {

  /*
   `findValues` is a protected method that invokes a macro to find all `Greeting` object declarations inside an `Enum`

   You use it to implement the `val values` member
  */
  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 (Hello, GoodBye, Hi, Bye)

// A safer alternative would be to use `withNameOption(name: String)` method which returns an Option[Greeting]
Greeting.withNameOption("Hello")

// => res1: Option[Greeting] = Some(Hello)

Greeting.withNameOption("Haro")

// => res2: Option[Greeting] = None

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).

More examples

Enum

Continuing from the enum declared in the quick-start section:

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.

Manual override of name

The first way to change the name behaviour is to manually override the def entryName: String method.

import enumeratum._

sealed abstract class State(override val 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")

Mixins to override the name

The second way to override the name behaviour is to mixin the stackable traits provided for common string conversions, Snakecase, UpperSnakecase, CapitalSnakecase, Hyphencase, UpperHyphencase, CapitalHyphencase, Dotcase, UpperDotcase, CapitalDotcase, Words, UpperWords, CapitalWords, 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")

ValueEnum

Asides from enumerations that resolve members from String names, Enumeratum also supports ValueEnums, enums that resolve members from simple values like Int, Long, Short, Char, Byte, and String (without support for runtime transformations).

These enums are not modelled after Enumeration from standard lib, and therefore have the added ability to make sure, at compile-time, that multiple members do not share the same value.

import enumeratum.values._

sealed abstract class LibraryItem(val value: Int, val name: String) extends IntEnumEntry

case object LibraryItem extends IntEnum[LibraryItem] {

  case object Book     extends LibraryItem(value = 1, name = "book")
  case object Movie    extends LibraryItem(name = "movie", value = 2)
  case object Magazine extends LibraryItem(3, "magazine")
  case object CD       extends LibraryItem(4, name = "cd")
  // case object Newspaper extends LibraryItem(4, name = "newspaper") <-- will fail to compile because the value 4 is shared

  /*
  val five = 5
  case object Article extends LibraryItem(five, name = "article") <-- will fail to compile because the value is not a literal
  */

  val values = findValues

}

assert(LibraryItem.withValue(1) == LibraryItem.Book)

LibraryItem.withValue(10) // => java.util.NoSuchElementException:

Restrictions

ValueEnums must have their value members implemented as literal values.

ScalaJS

In a ScalaJS project, add the following to build.sbt:

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

As expected, usage is exactly the same as normal Scala.

Play Integration

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

SBT

For enumeratum with full Play support:

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

Note that as of version 1.4.0, enumeratum-play for Scala 2.11 is compatible with Play 2.5+ while 2.10 is compatible with Play 2.4.x. Versions prior to 1.4.0 are compatible with 2.4.x.

Usage

PlayEnum

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._"`
*/


// You can also use the String Interpolating Routing DSL:

import play.api.routing.sird._
import play.api.routing._
import play.api.mvc._
Router.from {
    case GET(p"/hello/${Greeting.fromPath(greeting)}") => Action {
      Results.Ok(s"$greeting")
    }
}

PlayValueEnums

There are IntPlayEnum, LongPlayEnum, and ShortPlayEnum traits for use with IntEnumEntry, LongEnumEntry, and ShortEnumEntry respectively that provide Play-specific implicits as with normal PlayEnum. For example:

import enumeratum.values._

sealed abstract class PlayLibraryItem(val value: Int, val name: String) extends IntEnumEntry

case object PlayLibraryItem extends IntPlayEnum[PlayLibraryItem] {

  // A good mix of named, unnamed, named + unordered args
  case object Book     extends PlayLibraryItem(value = 1, name = "book")
  case object Movie    extends PlayLibraryItem(name = "movie", value = 2)
  case object Magazine extends PlayLibraryItem(3, "magazine")
  case object CD       extends PlayLibraryItem(4, name = "cd")

  val values = findValues

}

import play.api.libs.json.{ JsNumber, JsString, Json => PlayJson }
PlayLibraryItem.values.foreach { item =>
    assert(PlayJson.toJson(item) == JsNumber(item.value))
}

PlayFormFieldEnum

PlayEnum extends the trait PlayFormFieldEnum wich offers formField for mapping within a play.api.data.Form object.

import play.api.data.Form
import play.api.data.Forms._

object GreetingForm {
  val form = Form(
    mapping(
      "name"     -> nonEmptyText,
      "greeting" -> Greeting.formField
    )(Data.apply)(Data.unapply)
  )

  case class Data(
    name: String,
    greeting: Greeting)
}

Another alternative (if for example your Enum can't extend PlayEnum or PlayFormFieldEnum) is to create an implicit Format and bring it into scope using Play's of, i.e.

import play.api.data.Form
import play.api.data.Forms._

object Formats {
  implicit val greetingFormat = enumeratum.Forms.format(Greeting)
}

object GreetingForm {
  import Formats._

  val form = Form(
      mapping(
        "name"     -> nonEmptyText,
        "greeting" -> of[Greeting]
      )(Data.apply)(Data.unapply)
    )

    case class Data(
      name: String,
      greeting: Greeting)

}

Play JSON

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.

SBT

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

Note that as of version 1.4.0, enumeratum-play for Scala 2.11 is compatible with Play 2.5+ while 2.10 is compatible with Play 2.4.x. Versions prior to 1.4.0 are compatible with 2.4.x.

Usage

PlayJsonEnum

For example:

import enumeratum.{ PlayJsonEnum, Enum, EnumEntry }

sealed trait Greeting extends EnumEntry

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

}

PlayJsonValueEnum

There are IntPlayJsonEnum, LongPlayJsonEnum, and ShortPlayJsonEnum traits for use with IntEnumEntry, LongEnumEntry, and ShortEnumEntry respectively. For example:

import enumeratum.values._

sealed abstract class JsonDrinks(val value: Short, name: String) extends ShortEnumEntry

case object JsonDrinks extends ShortEnum[JsonDrinks] with ShortPlayJsonValueEnum[JsonDrinks] {

  case object OrangeJuice extends JsonDrinks(value = 1, name = "oj")
  case object AppleJuice  extends JsonDrinks(value = 2, name = "aj")
  case object Cola        extends JsonDrinks(value = 3, name = "cola")
  case object Beer        extends JsonDrinks(value = 4, name = "beer")

  val values = findValues

}

import play.api.libs.json.{ JsNumber, JsString, Json => PlayJson, JsSuccess }

// Use to deserialise numbers to enum members directly
JsonDrinks.values.foreach { drink =>
    assert(PlayJson.toJson(drink) == JsNumber(drink.value))
}
assert(PlayJson.fromJson[JsonDrinks](JsNumber(3)) == JsSuccess(JsonDrinks.Cola))
assert(PlayJson.fromJson[JsonDrinks](JsNumber(19)).isError)

Circe

SBT

To use enumeratum with Circe:

libraryDependencies ++= Seq(
    "com.beachape" %% "enumeratum-circe" % enumeratumVersion
)

To use with ScalaJS:

libraryDependencies ++= Seq(
    "com.beachape" %%% "enumeratum-circe" % enumeratumVersion
)

Usage

Enum

import enumeratum._

sealed trait ShirtSize extends EnumEntry

case object ShirtSize extends CirceEnum[ShirtSize] with Enum[ShirtSize] {

  case object Small  extends ShirtSize
  case object Medium extends ShirtSize
  case object Large  extends ShirtSize

  val values = findValues

}

import io.circe.Json
import io.circe.syntax._

ShirtSize.values.foreach { size =>
    assert(size.asJson == Json.fromString(size.entryName))
}

ValueEnum

import enumeratum.values._

sealed abstract class CirceLibraryItem(val value: Int, val name: String) extends IntEnumEntry

case object CirceLibraryItem extends IntEnum[CirceLibraryItem] with IntCirceEnum[CirceLibraryItem] {

  // A good mix of named, unnamed, named + unordered args
  case object Book     extends CirceLibraryItem(value = 1, name = "book")
  case object Movie    extends CirceLibraryItem(name = "movie", value = 2)
  case object Magazine extends CirceLibraryItem(3, "magazine")
  case object CD       extends CirceLibraryItem(4, name = "cd")

  val values = findValues

}

import io.circe.Json
import io.circe.syntax._

CirceLibraryItem.values.foreach { item =>
    assert(item.asJson == Json.fromInt(item.value))
}

UPickle

SBT

To use enumeratum with uPickle:

libraryDependencies ++= Seq(
    "com.beachape" %% "enumeratum-upickle" % enumeratumVersion
)

To use with ScalaJS:

libraryDependencies ++= Seq(
    "com.beachape" %%% "enumeratum-upickle" % enumeratumVersion
)

Usage

UPickleEnum works pretty much the same as CirceEnum and PlayJsonEnum variants, so we'll skip straight to the ValueEnum integration.

import enumeratum.values._

sealed abstract class ContentType(val value: Long, name: String) extends LongEnumEntry

case object ContentType
    extends LongEnum[ContentType]
    with LongUPickleEnum[ContentType] {

  val values = findValues

  case object Text  extends ContentType(value = 1L, name = "text")
  case object Image extends ContentType(value = 2L, name = "image")
  case object Video extends ContentType(value = 3L, name = "video")
  case object Audio extends ContentType(value = 4L, name = "audio")

}

import upickle.default.{ readJs, writeJs, Reader, Writer }
enum.values.foreach { entry =>
  val written = writeJs(entry)
  assert(readJs(written) == entry)
}

ReactiveMongo BSON

The enumeratum-reactivemongo-bson project is published separately and gives you access to ReactiveMongo's auto-generated boilerplate for BSON serialization in your Enum's.

SBT

libraryDependencies ++= Seq(
    "com.beachape" %% "enumeratum-reactivemongo-bson" % enumeratumVersion
)

Usage

ReactiveMongoBsonEnum

For example:

import enumeratum.{ ReactiveMongoBsonEnum, Enum, EnumEntry }

sealed trait Greeting extends EnumEntry

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

  val values = findValues

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

}

ReactiveMongoBsonValueEnum

There are IntReactiveMongoBsonValueEnum, LongReactiveMongoBsonValueEnum, and ShortReactiveMongoBsonValueEnum traits for use with IntEnumEntry, LongEnumEntry, and ShortEnumEntry respectively. For example:

import enumeratum.values._

sealed abstract class BsonDrinks(val value: Short, name: String) extends ShortEnumEntry

case object BsonDrinks extends ShortEnum[BsonDrinks] with ShortReactiveMongoBsonValueEnum[BsonDrinks] {

  case object OrangeJuice extends BsonDrinks(value = 1, name = "oj")
  case object AppleJuice  extends BsonDrinks(value = 2, name = "aj")
  case object Cola        extends BsonDrinks(value = 3, name = "cola")
  case object Beer        extends BsonDrinks(value = 4, name = "beer")

  val values = findValues

}

import reactivemongo.bson._

// Use to deserialise numbers to enum members directly
BsonDrinks.values.foreach { drink =>
  val writer = implicitly[BSONWriter[BsonDrinks, BSONValue]]

  assert(writer.write(drink) == BSONInteger(drink.value))
}

val reader = implicitly[BSONReader[BSONValue, BsonDrinks]]

assert(reader.read(BSONInteger(3)) == BsonDrinks.Cola)

Argonaut

SBT

To use enumeratum with Argonaut:

libraryDependencies ++= Seq(
    "com.beachape" %% "enumeratum-argonaut" % enumeratumVersion
)

Usage

Enum

import enumeratum._

sealed trait TrafficLight extends EnumEntry
object TrafficLight extends Enum[TrafficLight] with ArgonautEnum[TrafficLight] {
  case object Red    extends TrafficLight
  case object Yellow extends TrafficLight
  case object Green  extends TrafficLight
  val values = findValues
}

import argonaut._
import Argonaut._

TrafficLight.values.foreach { entry =>
    assert(entry.asJson == entry.entryName.asJson)
}

ValueEnum

import enumeratum.values._

sealed abstract class ArgonautDevice(val value: Short) extends ShortEnumEntry
case object ArgonautDevice
    extends ShortEnum[ArgonautDevice]
    with ShortArgonautEnum[ArgonautDevice] {
  case object Phone   extends ArgonautDevice(1)
  case object Laptop  extends ArgonautDevice(2)
  case object Desktop extends ArgonautDevice(3)
  case object Tablet  extends ArgonautDevice(4)

  val values = findValues
}

import argonaut._
import Argonaut._

ArgonautDevice.values.foreach { item =>
    assert(item.asJson == item.value.asJson)
}

Slick integration

Slick doesn't have a separate integration at the moment. You just have to provide a MappedColumnType for each database column that should be represented as an enum on the Scala side.

For example when you want the Enum[Greeting] defined in the introduction as a database column, you can use the following code

  implicit lazy val greetingMapper = MappedColumnType.base[Greeting, String](
    greeting => greeting.entryName,
    string => Greeting.withName(string)
  )

You can then define the following line in your Table[...] class

  // This maps a column of type VARCHAR/TEXT to enums of type [[Greeting]]
  def greeting = column[Greeting]("GREETING")

If you want to represent your enum in the database with numeric IDs, just provide a different mapping. This example uses the enum of type LibraryItem defined in the introduction:

  implicit lazy val libraryItemMapper = MappedColumnType.base[LibraryItem, Int](
    item => item.value,
    id => LibraryItem.withValue(id)
  )

Again you can now simply use LibraryItem in your Table class:

  // This maps a column of type NUMBER to enums of type [[LibaryItem]]
  def item = column[LibraryItem]("LIBRARY_ITEM")

Note that because your enum values are singleton objects, you may get errors when you try to use them in Slick queries like the following:

.filter(_.productType === ProductType.Foo)`

This is because ProductType.Foo in the above example is inferred to be of its unique type (ProductType.Foo) rather than ProductType, thus causing a failure to find your mapping. In order to fix this, simply assist the compiler by ascribing the type to be ProductType:

.filter(_.productType === (ProductType.Foo: ProductType))`

If you want to use slick interpolated SQL queries you need a few additional implicits.

implicit val greetingGetResult: GetResult[Greeting] = new GetResult[Greeting] {
  override def apply(positionedResult: PositionedResult): Greeting = Greeting.withName(positionedResult.nextString())
}

implicit val greetingOptionGetResult: GetResult[Option[Greeting]] = new GetResult[Option[Greeting]] {
  override def apply(positionedResult: PositionedResult): Option[Greeting] = positionedResult.nextStringOption().flatMap(Greeting.withNameOption)
}

implicit val greetingSetParameter: SetParameter[Greeting] = new SetParameter[Greeting] {
  override def apply(value: Greeting, positionedParameter: PositionedParameters): Unit =
    positionedParameter.setString(value.toString)
}

implicit val greetingOptionSetParameter: SetParameter[Option[Greeting]] = new SetParameter[Option[Greeting]] {
  override def apply(value: Option[Greeting], positionedParameter: PositionedParameters): Unit =
    positionedParameter.setStringOption(value.map(v => value.entryName))
}

Benchmarking

Benchmarking is in the unpublished benchmarking project. It uses JMH and you can run them in the sbt console by issuing the following command from your command line:

sbt +benchmarking/'jmh:run -i 10 -wi 10 -f3 -t 1'

The above command will run JMH benchmarks against different versions of Scala. Leave off + to run against the main/latest supported version of Scala.

On my late 2013 MBP using Java8 on OSX El Capitan:

[info] Benchmark                                            Mode  Cnt     Score    Error  Units
[info] EnumBenchmarks.indexOf                               avgt   30    11.628 ±  0.190  ns/op
[info] EnumBenchmarks.withNameDoesNotExist                  avgt   30  1809.194 ± 33.113  ns/op
[info] EnumBenchmarks.withNameExists                        avgt   30    13.540 ±  0.374  ns/op
[info] EnumBenchmarks.withNameOptionDoesNotExist            avgt   30     5.999 ±  0.037  ns/op
[info] EnumBenchmarks.withNameOptionExists                  avgt   30     9.662 ±  0.232  ns/op
[info] StdLibEnumBenchmarks.withNameDoesNotExist            avgt   30  1921.690 ± 78.898  ns/op
[info] StdLibEnumBenchmarks.withNameExists                  avgt   30    56.517 ±  1.161  ns/op
[info] values.ValueEnumBenchmarks.withValueDoesNotExist     avgt   30  1950.291 ± 29.292  ns/op
[info] values.ValueEnumBenchmarks.withValueExists           avgt   30     4.009 ±  0.062  ns/op
[info] values.ValueEnumBenchmarks.withValueOptDoesNotExist  avgt   30     5.285 ±  0.063  ns/op
[info] values.ValueEnumBenchmarks.withValueOptExists        avgt   30     6.621 ±  0.084  ns/op

Discussion

Other than the methods that throw NoSuchElementExceptions, performance is in the 10ns range (taking into account JMH overhead of roughly 2-3ns), which is acceptable for almost all use-cases. PRs that promise to increase performance are expected to be demonstrably faster.

Also, Enumeratum's withName is faster than the standard library's Enumeration, by around 4x in the case where an entry exists with the given name. My guess is this is because Enumeratum doesn't use any synchronized calls or volatile annotations. It is also faster in the case where there is no corresponding name, but not by a significant amount, perhaps because the high cost of throwing an exception masks any benefits.

Publishing

Projects are published independently of each other.

JVM + ScalaJS projects should have an aggregate project to make it easy to publish them, e.g. for enumeratum-circe:

$ sbt "project circe-aggregate" +clean +publish-signed

Should publish all needed artefacts. Note that sbt circe-aggregate/publish-signed will not work (ScalaJS gets skipped).

Enumeratum

Table of Contents

Quick start

SBT

Usage

More examples

Enum

Manual override of name

Mixins to override the name

ValueEnum

ScalaJS

Play Integration

SBT

Usage

PlayEnum

PlayValueEnums

PlayFormFieldEnum

Play JSON

SBT

Usage

PlayJsonEnum

PlayJsonValueEnum

Circe

SBT

Usage

Enum

ValueEnum

UPickle

SBT

Usage

ReactiveMongo BSON

SBT

Usage

ReactiveMongoBsonEnum

ReactiveMongoBsonValueEnum

Argonaut

SBT

Usage

Enum

ValueEnum

Slick integration

Benchmarking

Discussion

Publishing

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