How to create custom ReactiveMongo Reader & Writer for object?

Question

Let's say I have the following model:

case class Game(var _id: Option[BSONObjectID] = None,
                   name: String,
                   genre: Genre.Kind,
                   var created: Option[DateTime] = None,
                   var updated: Option[DateTime] = None
                  )

I want to store an instance of Game as follows: {"_id": "ObjectId(12345)", "name": "My Shooter Game", "genre": "Shooter", …}

For Genre I want to store the value as a String, but programmatically I want to deal with types and not values.

So here is what I thought would work:

object Genre {

  sealed trait Kind

  implicit val genreJsonFormat = Json.format[Genre.Kind]

  case object Shooter extends Kind {
    val name = "Shooter"

    override def toString = name
  }

  def getGenre(genre: String) = genre match {
    case Shooter.name => Shooter
    // ...
  }

  implicit object GenreWriter extends BSONDocumentWriter[Genre.Kind] {
    def write(genre: Genre.Kind): BSONDocument =
      BSONDocument("genre" -> genre.toString)
  }

  implicit object GenreReader extends BSONDocumentReader[Genre.Kind] {
    def read(doc: BSONDocument): Genre.Kind = Genre.getGenre(doc.getAs[String]("genre").get)
  }

}

Unfortunately, I get this compile error:

No unapply or unapplySeq function found

For:

implicit val genreJsonFormat = Json.format[Genre.Kind]

Any idea how I can achieve that?

score 0 · Answer 1 · answered Sep 10 '16 at 16:17

0

The macros from Play JSON do not yet support sealed family, so you have to do it the same way it's done for the BSON handlers.

answered Sep 10 '16 at 16:17

cchantep

9,118
3
30
41

It's recommanded to first read the [documentation](https://www.playframework.com/documentation/2.5.x/ScalaJson) – cchantep Sep 10 '16 at 18:01
`Json.format` is not provided by ReactiveMongo, but Play JSON – cchantep Sep 10 '16 at 22:08

How to create custom ReactiveMongo Reader & Writer for object?

1 Answers1