Is there any way to declare that a parameter to a function needs to be a type that is Serializable? ...

# serialization

[eygraber]

Is there any way to declare that a parameter to a function needs to be a type that is Serializable? For example:

fun persist(foo: ???) {
  Json.encodeToString(foo)
}

[edenman]

not that i know of. afaik it’s not knowable at compile time which is what you’re after

[jw]

Require the caller to supply a KSerializer

[edenman]

yeah, you still don’t know if that serializer is real until runtime tho

[edenman]

you can call KClass.serializer() on whatever class you want

[eygraber]

KClass.serializer is marked as InternalSerializationApi. Is there any other way to get a KSerializer?

[eygraber]

Oh I see there's one generated for each @Serializable type

[edenman]

forgot i was using the internal one. Jake is right, Foo.serializer() is probably your best bet

[jw]

Isn't it typed? So it would be fun <T> persist(foo: T, serializer: KSerializer<T>) { .. }

[eygraber]

I did something like this but the concept is the same. Haven't finished building it out yet, but it's looking like it will work:

interface RenderStateSerializer {
  fun <D> serialize(data: D, serializer: KSerializer<D>): ByteArray?
  fun <D> deserialize(data: ByteArray, deserializer: KSerializer<D>): D
}

[edenman]

yeah sorry i mean if someone (this guy) has opt-ed in to InternalSerializationApi then there’s nothing to prevent this from happening:

data class Foo(val bar: String)

fun taco() {
  val foo = Foo("foo")
  persist(foo, Foo:class.serializer())
}

[edenman]

which will happily compile and i believe crash at runtime

[jw]

@eygraber that is basically BinaryFormat

[eygraber]

Interesting. With BinaryFormat I would need a `serializersModule`which I don't believe I need for my use case