Add custom adapter to moshi

Question

I have an interface Data with a function called toData(). Different objects inherits from this Data.

Now I wrote an adapter which transform the result of toData() into an string

My custom adapter looks like this:

class Base64TypeAdapter {

    @FromJson
    fun fromJson(value: String?): ByteArray? {
        return value?.toByteArray()
    }

    @ToJson
    fun toJson(value: Data?): String? {
        return value?.toData()?.let { Base64.encodeToString(it.toByteArray(), Base64.NO_WRAP) }
    }
}

I created a Moshi builder

    private val proxyManMoshi = Moshi.Builder()
        .add(Base64ArrayTypeAdapter())
        .add(Base64TypeAdapter())
        .add(KotlinJsonAdapterFactory())
        .build()

    val dataAdapter = proxyManMoshi.adapter<Base64TypeAdapter>(Data::class.java)
  

But when I call dataAdapter.toJson() the input parameter is Base64TypeAdapter instead of Data.

How do I mount an adapter correctly?