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scalashapelesscirce

Get the underlying HList out from Circe

Is it possible to get the underlying hlist representation out from circe instead of the JSON? Essentially convert a case class to an HList

Note: I am aware that this can be achieved directly with shapeless, I would like to try circe's macro based parser, as I ran into performance issues with shapeless.

Solution

  • Why do you think that there is any "underlying hlist representation out from circe"?

    What circe does is parsing a String into JSON, introducing type classes Decoder and Encoder

    trait Encoder[A] extends Serializable { self =>
  def apply(a: A): Json
//...
}

trait Decoder[A] extends Serializable { self =>
  def apply(c: HCursor): Decoder.Result[A]
//...
}

    and deriving these type classes using shapeless. For example this means that if we have Decoder[H] and Decoder[T] then we have Decoder[H :: T]. But there is no underlying circe representation for a case class other than Json.

    circe doesn't convert a case class to an HList, shapeless does.