I have a data class in a module that is not depend...

# serialization

[marstran]

I have a data class in a module that is not dependent on kotlinx.serialization. Is there an easy way to make that class serializable in another module, without having to manually write the serializer?

[Dominaezzz]

Yes! Let me find you an example!

[Dominaezzz]

https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/custom_serializers.md#external-serializers-for-library-classes

[marstran]

Cool, thanks 🙂
But for some reason I’m getting this error while compiling: “java.lang.IllegalStateException: Class ColourEffect have constructor parameters which are not properties and therefore it is not serializable automatically”.

I did this:

@Serializer(forClass = ColourEffect::class)
object ColourEffectSerializer {}

@Serializable
data class Wrapper(@Serializable(with = ColourEffectSerializer::class) val colourEffect: ColourEffect)

[marstran]

And ColourEffect looks like this:

data class ColourEffect(
    val u: Int,
    val v: Int
) {

    init {
        require(u in 0..255)
        require(v in 0..255)
    }

}

[marstran]

Any idea why that happens?

[Dominaezzz]

Hmm, no idea.

[marstran]

Almost feels like a bug. I made a data class in the same module and created a serializer for it the same way, and that worked well.

[Nagarajan]

I was also facing same issue. Try UseSerializer file annotation that's kinda solved the issue

[marstran]

@Nagarajan Oh, thanks. I’ll try that.