map serialisation

[Michel Daviot]

Hi,

Is there a way to serialise directly a map like this one ?

val m=Map("a"->3, "b"->"c")

m: scala.collection.immutable.Map[String,Any] = Map(a -> 3, b -> c)

Json(m)

<console>:15: error: Cannot serialize type scala.collection.immutable.Map[String,Any] to rapture.json.Json. Please provide an implicit Serializer of type scala.collection.immutable.Map[String,Any].

I found a workaround using json interpolator like that :

 def toJsonObject: Json =

    json"""{ 

      "klass_id": $klassId, 

      "name":$name , 

      "cardstring":$cardString  }"""

But it might be possible to implement a serialiser for a Map[String, Any] by using proper serialisers based on runtime type and value.toString for the rest. What do you think ?

[Jon Pretty]

Hi Michel,

That's not so straightforward because it relies on runtime types, so we'll have to create a custom serializer to dispatch to other serializers as appropriate. This works, but you'll need to add cases for all types you want to serialize:

  implicit val anySerializer: rapture.data.Serializer[Any, Json] =
    Json.serializer[Json].contramap {

      case s: String => Json(s)

      case i: Int => Json(i)

      case d: Double => Json(d)
    }

  val json = Json(Map("foo" -> "bar", "baz" -> 42))

That might look very redundant with the right-hand side of all the cases being the same, but each of those calls to `Json(foo)` is pulling in a different implicit `Serializer` of its own based on the type matched on the LHS.

Does that work?

Cheers,
Jon

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Jon Pretty | @propensive

[Michel Daviot]

Yep, that's fine, thanks a lot !