so `get().body<List<Class>>()` apparen...

# ktor

[S.]

so get().body<List<Class>>() apparently also expects the json input to be an array and when it only returns one object I always run into kotlinx.serialization.json.internal.JsonDecodingException: Expected start of the array '[', but had 'EOF' instead
is there a way around this other than catching the exception and .body<Class> ?

[Aleksei Tirman [JB]]

So an endpoint may return a JSON array or object?

[S.]

Yes.

it's like this:

get("{id...}") {
            call.respond(call.parameters.getAll("id")?.map {
                WordService.fetchById(
                    it.toIntOrNull() ?: return@get call.respondText(
                        INVALID_ID,
                        status = HttpStatusCode.BadRequest
                    )
                ) ?: return@get call.respondText("No word with id $it", status = HttpStatusCode.NotFound)
            } ?: return@get call.respondText("No ids specified", status = HttpStatusCode.BadRequest))
        }

with only one id parameter it sends the single element of the list as an object

[Paul Woitaschek]

Then let it return a JsonElement and do your magic based on that

[S.]

sorry but how would I do this with ktor?

[phldavies]

initially you'd need to get the JsonElement from ktor using .get().body<JsonElement>() and then use something that would handle the decoding of both a JsonArray and a JsonObject to a List<MyClass> . Something similar to this might help:

private inline fun <reified T> JsonElement.asListOf(serializer: KSerializer<T> = serializer()) =
    when (this) {
        is JsonObject -> listOf(Json.decodeFromJsonElement(serializer, this))
        is JsonArray -> Json.decodeFromJsonElement(ListSerializer(serializer), this)
        else -> error("Unexpected element type - expected object or array")
    }

which would allow you to do .body<JsonElement>().asListOf<MyClass>()