---
title: "Sealed Enum"
source: "/sealed-enum/"
---

sealed enum

# An open source Kotlin annotation processor for replacing enum classes with sealed classes of objects.

## Why we built it.

In Kotlin, sealed classes are more powerful and more flexible than enums, but enums can still do some things that sealed classes can't. We recognized that a sealed class of objects is strictly more powerful than enums, given a bit of repeated boilerplate code:

            `sealed class Alpha {     object Beta : Alpha()     object Gamma : Alpha()      @GenSealedEnum     companion object }  println(Beta.ordinal) // 0 println(Beta.name) // "Beta" println(Alpha.values) // [Alpha$Beta@491cc5c9, Alpha$Gamma@74ad1f1f] println(Alpha.valueOf("Beta")) // Alpha$Beta@491cc5c9`

`sealed-enum` generates that boilerplate code automatically, so we can replace enums and gain all of the benefits of using sealed classes without the tedious and error-prone maintenance of boilerplate.

## How it works.

If the companion object of any sealed class of objects is annotated with `@GenSealedEnum`, `sealed-enum` will generate code that allows using the sealed class like an enum. Extension properties are generated for the objects (`ordinal` and `name`), as well as the sealed class's companion object (`values`, `valueOf`). These extension properties are backed by an `object` implementing `SealedEnum`, which provides a generic interface that is more convenient that generically handling normal enum classes.

Additional features include specifying the traversal order of sealed class hierarchies, creating a `SealedClass` object from normal enum classes, and generating isomorphic enum classes for sealed enums.

## How to use it.

### 0) Add dependencies to Gradle via Jitpack

Via `kapt`:

            `plugins {     kotlin("kapt") }  repositories {     maven(url = "https://jitpack.io") }  dependencies {     implementation("com.github.livefront.sealed-enum:sealedenum:VERSION")     kapt("com.github.livefront.sealed-enum:sealedenumprocessor:VERSION") }`

Via `ksp`:

            `plugins {     id("com.google.devtools.ksp") version "1.8.0-1.0.9" }  repositories {     maven(url = "https://jitpack.io") }  dependencies {     implementation("com.github.livefront.sealed-enum:runtime:0.7.0")     ksp("com.github.livefront.sealed-enum:ksp:0.7.0") }`

Check out the project on [Github](https://github.com/livefront/sealed-enum) for the latest version information.

### 1) Annotate the companion object of a sealed class with @GenSealedEnum

            `sealed class Alpha {     object Beta : Alpha()     object Gamma : Alpha()      @GenSealedEnum     companion object }`

Use the generated extension methods:

            `println(Beta.ordinal) // 0  println(Alpha.values) // [Alpha$Beta@491cc5c9, Alpha$Gamma@74ad1f1f]`

The `SealedEnum` implementation can be retrieved with `Alpha.sealedEnum`, and backs the other extensions properties and methods:

                `object AlphaSealedEnum : SealedEnum<Alpha> {     override val values: List<Alpha> = listOf(         Alpha.Beta,         Alpha.Gamma     )      override fun ordinalOf(obj: Alpha): Int = when (obj) {         Alpha.Beta -> 0         Alpha.Gamma -> 1     }      override fun nameOf(obj: AlphaSealedEnum): String = when (obj) {         Alpha.Beta -> "Alpha_Beta"         Alpha.Gamma -> "Alpha_Gamma"     }      override fun valueOf(name: String): AlphaSealedEnum = when (name) {         "Alpha_Beta" -> Alpha.Beta         "Alpha_Gamma" -> Alpha.Gamma         else -> throw IllegalArgumentException("""No sealed enum constant $name""")     } }`

Check out the project on [Github](https://github.com/livefront/sealed-enum) for more detailed usage instructions.

## Built by Livefront.

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