Hey! I have a generic data class and I keep getting this error: `Serializer for class 'GetPaginatedR...

# serialization

[Ruben Quadros]

Hey! I have a generic data class and I keep getting this error:
Serializer for class 'GetPaginatedResponse' is not found

This is my data class

@Serializable(with = GetPaginatedResponseSerializable::class)
data class GetPaginatedResponse(val isNext: Boolean, val content: T)

More info in 🧵

[Ruben Quadros]

I have tried a custom serializer but it doesnt work

class GetPaginatedResponseSerializable<T>(private val tSerializer: KSerializer<T>) : KSerializer<GetPaginatedResponse<T>> {

    private val paginatedResponseSerializer = GetPaginatedResponse.serializer(tSerializer)

    override val descriptor: SerialDescriptor
        get() = SerialDescriptor("GetPaginatedResponseSerializable", paginatedResponseSerializer.descriptor)

    override fun deserialize(decoder: Decoder): GetPaginatedResponse<T> {
        val paginatedResponse = decoder.decodeSerializableValue(paginatedResponseSerializer)
        val isNext = paginatedResponse.isNext
        val content = paginatedResponse.content

        return GetPaginatedResponse(
            isNext = isNext,
            content = content
        )
    }

    override fun serialize(encoder: Encoder, value: GetPaginatedResponse<T>) {
        encoder.encodeSerializableValue(paginatedResponseSerializer, GetPaginatedResponse(value.isNext, value.content))
    }
}

[Adam S]

It looks like you're using the serializer recursively

[Adam S]

The custom serializer class tries to fetch itself

[Adam S]

Serializing generic content can be hard. What sort of values can the content property be? Primitives, or objects, or lists? Are the possible values ones you have declared yourself, or are they external?

[Ruben Quadros]

It will mostly be lists. List<SomeType>

[Ruben Quadros]

Yes they are declared by myself

[Adam S]

Ah okay, that's good. It's generally easier to used closed-polymorphism instead of open-polymorphism.

I'd create a sealed interface parent for your SomeType, and change GetPaginatedResponse so it's not generic, but instead just uses SomeTypeParent.

@Serializable
data class GetPaginatedResponse(
  val isNext: Boolean,
  val content: SomeTypeParent,
)

Because SomeParentType is sealed, the possible values are limited, and KxS will be more easily able to encode/decode.

[Ruben Quadros]

Okay and doing this will eliminate the need for custom serializer as well?