polymorphism-sealed.md

Closed Polymorphism

https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/polymorphism.md#closed-polymorphism

Static types

@Serializable
open class Project(val name: String)

class OwnedProject(name: String, val owner: String) : Project(name)

fun main() {
  val tsGenerator = KxsTsGenerator()
  println(tsGenerator.generate(Project.serializer()))
}

You can get the full code here.

Since OwnedProject is not @Serializable, only the properties of Project generated.

export interface Project {
  name: string;
}

import kotlinx.serialization.modules.*

@Serializable
abstract class Project {
  abstract val name: String
}

@Serializable
class OwnedProject(override val name: String, val owner: String) : Project()

val module = SerializersModule {
  polymorphic(Project::class) {
    subclass(OwnedProject::class)
  }
}

fun main() {
  val config = KxsTsConfig(serializersModule = module)

  val tsGenerator = KxsTsGenerator(config)

  println(tsGenerator.generate(Project.serializer()))
}

You can get the full code here.

export type Project = any;
// export interface Project {
//   name: string;
// }
//
// export interface OwnedProject extends Project {
//   name: string;
//   owner: string;
// }

Sealed classes

Sealed classes are the best way to generate TypeScript interface so far, because all subclasses are defined in the SerialDescriptor.

A sealed class will be converted as a union enum, with enum member types .

This has many benefits that closely match how sealed classes work in Kotlin.

@Serializable
sealed class Project {
  abstract val name: String
}

@Serializable
@SerialName("OProj")
class OwnedProject(override val name: String, val owner: String) : Project()

@Serializable
class DeprecatedProject(override val name: String, val reason: String) : Project()

fun main() {
  val tsGenerator = KxsTsGenerator()
  println(tsGenerator.generate(Project.serializer()))
}

You can get the full code here.

export type Project =
  | Project.DeprecatedProject
  | Project.OProj;

export namespace Project {
  export enum Type {
    DeprecatedProject = "dev.adamko.kxstsgen.example.examplePolymorphicSealedClass01.DeprecatedProject",
    OProj = "OProj",
  }

  export interface DeprecatedProject {
    type: Project.Type.DeprecatedProject;
    name: string;
    reason: string;
  }

  export interface OProj {
    type: Project.Type.OProj;
    name: string;
    owner: string;
  }
}

Nested sealed classes

Nested sealed classes are 'invisible' to Kotlinx Serialization. In this example, sealed class Retriever is ignored.

For now, it's recommended to avoid nested sealed classes.

@Serializable
sealed class Dog {
  abstract val name: String

  @Serializable
  @SerialName("Dog.Mutt")
  class Mutt(override val name: String, val loveable: Boolean = true) : Dog()

  @Serializable
  sealed class Retriever : Dog() {
    abstract val colour: String

    @Serializable
    @SerialName("Dog.Retriever.Golden")
    data class Golden(
      override val name: String,
      override val colour: String,
      val cute: Boolean = true,
    ) : Retriever()

    @Serializable
    @SerialName("Dog.Retriever.NovaScotia")
    data class NovaScotia(
      override val name: String,
      override val colour: String,
      val adorable: Boolean = true,
    ) : Retriever()
  }
}

fun main() {
  val tsGenerator = KxsTsGenerator()
  println(tsGenerator.generate(Dog.serializer()))
}

You can get the full code here.

export type Dog =
  | Dog.Golden
  | Dog.Mutt
  | Dog.NovaScotia;

export namespace Dog {
  export enum Type {
    Mutt = "Dog.Mutt",
    Golden = "Dog.Retriever.Golden",
    NovaScotia = "Dog.Retriever.NovaScotia",
  }

  export interface Mutt {
    type: Dog.Type.Mutt;
    name: string;
    loveable?: boolean;
  }

  export interface Golden {
    type: Dog.Type.Golden;
    name: string;
    colour: string;
    cute?: boolean;
  }

  export interface NovaScotia {
    type: Dog.Type.NovaScotia;
    name: string;
    colour: string;
    adorable?: boolean;
  }
}
// Nested sealed classes don't work at the moment :(
// export type Dog = Dog.Mutt | Dog.Retriever
//
// export namespace Dog {
//   export enum Type {
//     Mutt = "Mutt",
//   }
//
//   export interface Mutt {
//     type: Type.Mutt;
//     name: string;
//     loveable?: boolean;
//   }
//
//   export type Retriever = Retriever.Golden | Retriever.NovaScotia
//
//   export namespace Retriever {
//     export enum Type {
//       Golden = "Golden",
//       NovaScotia = "NovaScotia",
//     }
//
//     export interface Golden {
//       type: Type.Golden;
//       name: string;
//       cute?: boolean;
//     }
//
//     export interface NovaScotia {
//       type: Type.NovaScotia;
//       name: string;
//       adorable?: boolean;
//     }
//   }
// }

Objects

@Serializable
sealed class Response

@Serializable
object EmptyResponse : Response()

@Serializable
class TextResponse(val text: String) : Response()

fun main() {
  val tsGenerator = KxsTsGenerator()
  println(
    tsGenerator.generate(Response.serializer())
  )
}

You can get the full code here.

export type Response =
  | Response.EmptyResponse
  | Response.TextResponse;

export namespace Response {
  export enum Type {
    EmptyResponse = "dev.adamko.kxstsgen.example.examplePolymorphicObjects01.EmptyResponse",
    TextResponse = "dev.adamko.kxstsgen.example.examplePolymorphicObjects01.TextResponse",
  }

  export interface EmptyResponse {
    type: Response.Type.EmptyResponse;
  }

  export interface TextResponse {
    type: Response.Type.TextResponse;
    text: string;
  }
}