hiya, I am a very new to kotlinJS and have a quest...

# javascript

[Robert Munro]

hiya, I am a very new to kotlinJS and have a question regarding transporting casting objects sent over http - from the server i send a Response

@Serializable
data class ResponseDomain constructor(
    val payload: List<Domain> = listOf(),
    val errors: List<ErrorDomain> = listOf()
)

where domain is a kotlin interface that all the domain data obects implement and they are serialized using kotlin serialization(polymorphic)
In my frontend I fetch the url like so:

val response = window
    .fetch("$BASE_URL/playlists")
    .await()
    .json()
    .await()

which has a payload of List<PlaylistDomain>

@Serializable
data class PlaylistDomain constructor(
    val id: Long? = null,
    val title: String,
    val items: List<PlaylistItemDomain> = listOf(),
    ...
) : Domain

but casting back to ResponseDomain fails

(response as ResponseDomain)

with and Illegal cast error

should i just send the response as text/plain (not application/json) and use kotlin deserialisation to get a ResponseDomain?
seems like since the browser parses my json to json object i seem to not be able to cast to my kotlin object type - obvs i dont want to map the whole thing from json to domain manually but in the kotlin js tutorial (the video browser one) they map the response as a cast (response as Video). maybe it only works for simple objects?

[Robert Munro]

so this works ...

val response = window
    .fetch("$BASE_URL/playlists")
    .await()
    .text()
    .await()

deserialiseResponse(response).let {
    it.payload as List<PlaylistDomain>
}

if anyone has options on wearther or not this is the best way then i would be interested to know 🙂

[Robert Jaros]

kotlinx.serialization is the only option if you want to get Kotlin classes