Custom multipart-form-data serializable in Kotlin/Ktor - kotlin

Question

Does anyone know how to program the override function convertForReceive of a custom Multipart.FormData converter?
I want to convert the multipart request to my class with the converter but I don't know how it works.
I have:
Application.kt
install(ContentNegotiation) {
json()
register(ContentType.MultiPart.FormData, CustomMultipartConverter)
}
CustomMultipartConverter
object CustomMultipartConverter: ContentConverter {
override suspend fun convertForReceive(context: PipelineContext<ApplicationReceiveRequest, ApplicationCall>): Any? {
TODO("Not yet implemented")
}
override suspend fun convertForSend(
context: PipelineContext<Any, ApplicationCall>,
contentType: ContentType,
value: Any
): Any? {
TODO("Not yet implemented")
}
}
REQUEST CLASS
class CreatePostRequest(
val text: String,
val image: File? = null
)
ROUTE
route("v1/posts") {
authenticate {
route("create") {
val authJWT = call.authentication.principal as JWTAtuh
val request = call.receive<CreatePostRequest>()
//myCode
call.respond(HttpStatusCode.OK)
}
}
}

Answer 1

You can take SerializationConverter as a reference:
override suspend fun convertForReceive(context: PipelineContext<ApplicationReceiveRequest, ApplicationCall>): Any? {
val request = context.subject
val channel = request.value as? ByteReadChannel ?: return null
val charset = context.call.request.contentCharset() ?: defaultCharset
val serializer = format.serializersModule.serializer(request.typeInfo)
val contentPacket = channel.readRemaining()
return when (format) {
is StringFormat -> format.decodeFromString(serializer, contentPacket.readText(charset))
is BinaryFormat -> format.decodeFromByteArray(serializer, contentPacket.readBytes())
else -> {
contentPacket.discard()
error("Unsupported format $format")
}
}
}