How do I define value of discriminator for coproduct codecs?

Question

Could you please explain how coproducts really work? Here is my code

sealed trait ArdbData

case class ArdbDataString(value: String) extends ArdbData

case class ArdbDataLong(value: Long) extends ArdbData

case class ArdbDataDouble(value: Double) extends ArdbData

object ArdbDataString {
  implicit val codec: Codec[ArdbDataString] = // ... some codec here
  implicit val discriminator: Discriminator[ArdbData, ArdbDataString, Int] = Discriminator(6)
}

object ArdbDataLong {

  implicit val codec: Codec[ArdbDataLong] = // ... some codec here
  implicit val discriminator: Discriminator[ArdbData, ArdbDataLong, Int] = Discriminator(1)
}

object ArdbDataDouble {
  implicit val codec: Codec[ArdbDataDouble] = // ... some codec here
  implicit val discriminator: Discriminator[ArdbData, ArdbDataDouble, Int] = Discriminator(2)
}

object ArdbData {
  implicit val discriminated: Discriminated[ArdbData, Int] = Discriminated(uint8)

  import shapeless.syntax.singleton._

//  implicit val codec: Codec[ArdbData] = Codec.coproduct[ArdbData].discriminatedBy(uint8).using(
//    'ArdbDataString ->> 4 :: 'ArdbDataLong ->> 1 :: 'ArdbDataDouble ->> 2 :: HNil)
}

I thought I have to define coproduct codec for ArdbData as demonstrated in this test. Also I need to use particular IDs for each subtype which I defined in discriminatedBy.using(). When I started testing it I suddenly found keys from .using are not used. Instead ID from each Discriminator instance is used. Then I commented out Codec.coproduct[ArdbData] and it still compiles! Why does it compile ? What's the right way of defining value of discriminator ?

How do I define value of discriminator for coproduct codecs?

0 Answers0