Say you have JSON with a field that contains a `Li...

# serialization

[Justin]

Say you have JSON with a field that contains a List<Any?>.

In practice, the Any? can be (a) null, (b) a String, (c) an Int, or (d) another `List<Any?>.

What's the best practice for deserializing this with kotlinx.serialization?

Currently, I'm doing @ContextualSerialization like this:

@Serializable
data class Items(
    val id: Int,
    val values: List<@ContextualSerialization Any?> = emptyList()
)

This seems like the right direction, except I'm not sure how to get from this to an array of usable types (e.g. String, Int, List<Any>)?

[Dominaezzz]

@Serializable
data class Items(
    val id: Int,
    val values: JsonArray
)

?

[Justin]

@Dominaezzz That works, but from there, how do I deserialize the different types of values that appear in that values array into their actual types (when it could be a string, int, or list)?

[Justin]

this is sort of what i want to do

[Justin]

@Serializable
data class Items(
    val id: Int,
    @Polymorphic val values: Value? = null
) {
    sealed class Value {
        @Serializable
        data class Array(val index: Int, val string: String? = null)

        @Serializable
        data class String(val text: String? = null)

        @Serializable
        data class Int(val index: Int? = null)
    }
}

[Dominaezzz]

Was about to suggest that.

[Dominaezzz]

I think that's the way to go.

[Justin]

i'll try that

[Justin]

i think i tried it earlier and it didn't quite work

[Justin]

because how do i get from the raw array case to the Array type (which just pulls the values out of the array)

[Dominaezzz]

With a custom serializer, just cast the Decoder to a JsonInput and call decodeJson(), then you can inspect the small part of the json tree.

[Dominaezzz]

@Polymorphic wont help here.

[Justin]

what about @ContextualSerialization

[Justin]

part of the problem is that the field is nullable

[Dominaezzz]

You don't need it.

[Justin]

and the values in the array case are also nullable

[Dominaezzz]

Just specify the serializer statically.

[Justin]

hmm