Play JSON Reads

carMotor.scala

  implicit lazy val reads: Reads[CarMotor] = {

    import play.api.libs.json._
    import play.api.libs.functional.syntax._

    (__ \ "engineType").read[String].flatMap {
      case "electric" =>
        Reads.pure(Electric)
      case "engine" => {
        (__ \ "fuel").read[CarFuelType] and
        (__ \ "engineSize").readNullable[CarEngineSize] and
        (__ \ "co2").readNullable[Int]
      }.apply(Engine.apply _)
      case _ =>
        Reads(_ => JsError("error.invalid"))
    }
  }

  implicit lazy val reads2: Reads[CarMotor] = {

    import play.api.libs.json._
    import play.api.libs.functional.syntax._

    val electrical: Reads[CarMotor] = __.read[String].map(_ => Electric)

    val engine: Reads[CarMotor] = {
      (__ \ "fuel").read[CarFuelType] and
      (__ \ "engineSize").readNullable[CarEngineSize] and
      (__ \ "co2").readNullable[Int]
    }.apply(Engine.apply _)

    electrical | engine
  }