I’m following along with <https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/polymorph...

# serialization

[Landry Norris]

I’m following along with https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/polymorphism.md#objects and I found that the list of multiple objects caused the type to show up, but if I only had EmptyResponse, then the output would just be [{}]. Is there a way to force it to give the type when there’s only one object?

[Landry Norris]

A list of two EmptyResponse gave [{}, {}], but if I made a second object and used both, it would give the types.

[Dominaezzz]

Code snippet? I'm 99.99% sure I know what's wrong.

[ephemient]

yep. symptom sounds you're calling the serializer with the wrong reified type.

[Landry Norris]

I’m calling Json.encodeToString(listOf(EmptyResponse, EmptyResponse)) . This is currently only for encoding. I’m not decoding it yet.

[Dominaezzz]

Json.encodeToString(listOf<BaseClass>(EmptyResponse, EmptyResponse))

[Landry Norris]

Same result with Json.encodeToString(EmptyResponse)

[Landry Norris]

I’ll look at that.

[Dominaezzz]

Json.encodeToString<BaseClass>(EmptyResponse)

[Landry Norris]

That works.

[ephemient]

also

val list: List<BaseClass> = listOf(EmptyResponse)
Json.encodeToString(list)

and all sorts of other variations

[Landry Norris]

Interesting. Why does it require that I explicitly mark it as Response?

[ephemient]

because Kotlin infers the narrowest possible type for listOf(EmptyResponse) unless it has another reason to, which is List<EmptyResponse>, which is not polymorphic

[ephemient]

I would tend to avoid the reified helper functions in kotlinx.serialization anyway, due to the need for reflection to obtain the serializer (waiting on https://github.com/Kotlin/kotlinx.serialization/issues/1348)

[Landry Norris]

That makes sense. I guess I’ll have to be careful when I work with polymorphic serializers. I noticed that even when I used a serializerModule, it would still happen. I would have assumed that the fact that I marked EmptyClass as a subclass would tell it to use polymorphism.

[ephemient]

no, EmptyClass is only polymorphic in the context of a BaseClass

[ephemient]

you can register a class as belonging to multiple polymorphic hierarchies

[Landry Norris]

That makes sense.