my example won't compile

[jarlah]

The example below won't compile. Fails with this message:

[error]   could not find Lazy implicit value of type julienrf.json.derived.DerivedReads[A]
[error]   implicit lazy val format: OFormat[Event] = flat.oformat((__ \ "type").format[String])
[error]                                                          ^
[error] one error found
[error] (compile:compileIncremental) Compilation failed
[error] application -

! @70h4nj2oc - Internal server error, for (POST) [/] ->

play.sbt.PlayExceptions$CompilationException: Compilation error[could not find Lazy implicit value of type julienrf.json.derived.DerivedReads[A]]
    at play.sbt.PlayExceptions$CompilationException$.apply(PlayExceptions.scala:27)
    at play.sbt.PlayExceptions$CompilationException$.apply(PlayExceptions.scala:27)
    at scala.Option.map(Option.scala:145)
    at play.sbt.run.PlayReload$$anonfun$taskFailureHandler$1.apply(PlayReload.scala:49)
    at play.sbt.run.PlayReload$$anonfun$taskFailureHandler$1.apply(PlayReload.scala:44)
    at scala.Option.map(Option.scala:145)
    at play.sbt.run.PlayReload$.taskFailureHandler(PlayReload.scala:44)
    at play.sbt.run.PlayReload$.compileFailure(PlayReload.scala:40)
    at play.sbt.run.PlayReload$$anonfun$compile$1.apply(PlayReload.scala:17)
    at play.sbt.run.PlayReload$$anonfun$compile$1.apply(PlayReload.scala:17)

Do I have to implement standard Json.format[Event] formatter in addition?

import play.api.mvc.{Action, BodyParsers, Controller}
import play.api.libs.json._
import julienrf.json.derived._
import scala.concurrent.Future
import Event._

class EventController extends Controller {

  def insert() = Action.async(BodyParsers.parse.json) { request =>
    request.body.validate[Event].asEither match {
      case Right(event) => println(event)
      case Left(error) => println(error.mkString)
    }
    Future.successful(Ok)
  }
}

sealed trait Event {
  val id: Option[Long]
  val links: Option[Seq[String]]
  val note: Option[String]
}

object Event {
  implicit lazy val format: OFormat[Event] = flat.oformat((__ \ "type").format[String])
}

case class Move(
  id: Option[Long],
  links: Option[Seq[String]],
  note: Option[String]
) extends Event

case class Control(
  id: Option[Long],
  links: Option[Seq[String]],
  note: Option[String]
) extends Event

[julienrf]

Hi, that’s a known limitation of knownDirectSubclasses: you have to move the Event object after all the class definitions that extend Event.

[jarlah]

thanks so much :)