<@UFT11FKSP> ```@Serializable data class SuccessRe...

# kvision

[Wishnuprathikantam]

@Robert Jaros

@Serializable
data class SuccessResponse<T>(
        val status: Int,
        val data: T,
        val message: String
) : ApiResponse()

@Serializable
data class ErrorResponse(
        val status: Int,
        val errorCode: Int,
        val message: String
) : ApiResponse()

@Serializable
sealed class ApiResponse

remoteCall(
                ApiRoutes.LOGIN,
                Json.encodeToString(AdminRequest.serializer(), body),
                ApiResponse.serializer(),
                <http://HttpMethod.POST|HttpMethod.POST>
        )

when (this) {
    is SuccessResponse<*> -> {
        val data = this.unsafeCast<SuccessResponse<T>>()
        success(data)
    }
    is ErrorResponse -> {
        failure(this)
    }
    else -> {
        console.log(this)
    }
}

Need help with deserializing sealed classes, without else block throws NoWhenBranchMatchedException

[Arslan Armanuly]

What type does this have?

[Wishnuprathikantam]

ApiResponse

[Robert Jaros]

Are you on IR backend?

[Wishnuprathikantam]

No

[Arslan Armanuly]

I have tested this case in my own js project(with no IR), but its seems there is no compilation error being thrown. Are you sure there is only two subclasses of ApiResponse?

[Wishnuprathikantam]

Yes

[Robert Jaros]

Can you check in DevTools how does the raw (json) response look like?

[Robert Jaros]

the error shows there is probably 'null' value in json

[Robert Jaros]

it looks like the serialization problem on the backend side? what do you use?

[Wishnuprathikantam]

{
  "status": 200,
  "data": {
    "hash": "<http://MTIzNDU2Nzg5.MQ|MTIzNDU2Nzg5.MQ>==..",
    "key": "eyJhbGciOiJIUzUxMiJ9.."
  },
  "message": "",
  "httpStatusCode": 200
}

[Wishnuprathikantam]

ktor with gson

[Arslan Armanuly]

I guess the problem lies in the usage of generic, because it can't deserialize the "data"

[Arslan Armanuly]

I tried to deserialize a simple object but got

[Arslan Armanuly]

basically same error

[Wishnuprathikantam]

@Arslan Armanuly yes

[Robert Jaros]

I think gson serialization is not compatible with kotlinx deserialization

[Robert Jaros]

it doesn't generate class descriptor

[Robert Jaros]

you should try ktor with kotlinx.serialization instead of gson

[Arslan Armanuly]

I am using kotlinx.serialization instead of gson but having same error

[Arslan Armanuly]

I guess it is problem of serialization and should be redirected to the #serialization

[Wishnuprathikantam]

https://github.com/Kotlin/kotlinx.serialization/issues/944

[Wishnuprathikantam]

https://stackoverflow.com/questions/64826750/how-do-i-serialize-a-generic-sealed-class-with-kotlinx-serialization

[Arslan Armanuly]

I guess the workaround is to have data as String and deserialize it after the when

[Wishnuprathikantam]

I'll try

[Wishnuprathikantam]

@Arslan Armanuly Same error guess need to add this

private val module = SerializersModule {
        polymorphic(ApiResponse::class) {
            subclass(SuccessResponse::class)
            subclass(ErrorResponse::class)
        }
    }
 private val client = RestClient(module)

[Wishnuprathikantam]

@Robert Jaros no constructor for RestClient(SerializersModule) ?

[Robert Jaros]

It is available in 4.0.0

[Wishnuprathikantam]

Okay, ⬆️ Upgrading to 4.0.0

[Robert Jaros]

I've managed to get polymorphic deserialization with generic class working (with kotlinx serialization and deserialization)

[Robert Jaros]

this is my example code:

@Serializable
data class SuccessResponse<T>(
    val status: Int,
    val data: T,
    val message: String
) : ApiResponse<T>()

@Serializable
data class ErrorResponse<T>(
    val status: Int,
    val errorCode: Int,
    val message: String
) : ApiResponse<T>()

@Serializable
sealed class ApiResponse<T>

@Serializable
data class Data(val hash: String, val key: String)

[Robert Jaros]

I've added T to the ApiResponse

[Robert Jaros]

And then:

val responseModule = SerializersModule {
                polymorphic(ApiResponse::class) {
                    subclass(SuccessResponse.serializer(PolymorphicSerializer(Any::class)))
                }
                polymorphic(Any::class) {
                    subclass(Data::class)
                }
            }

[Robert Jaros]

val source = SuccessResponse(5, Data("h", "k"), "message")
            val json = Json {
                serializersModule = responseModule
            }.encodeToString(
                ApiResponse.serializer(Data.serializer()),
                source
            )
            console.log(json)
            val x = Json { serializersModule = responseModule }.decodeFromString(
                ApiResponse.serializer(Data.serializer()),
                json
            )
            console.log(x)

[Robert Jaros]

I think you could use this to get what you wanted if you get kotlinx.serialization on the Ktor side. The generated json looks like this:

{
  "type": "com.example.SuccessResponse",
  "status": 5,
  "data": {
    "type": "com.example.Data",
    "hash": "h",
    "key": "k"
  },
  "message": "message"
}

[Robert Jaros]

of course you need to register serializers for all T you use

[Wishnuprathikantam]

@Robert Jaros Thanks a lot! I'll update ktor backend to use kotlinx serialization.