Scala macro to generate a sealed trait's sub classes. This macro will generate a function (className: String, jsonString: String) => Option[A]. Depends on shapeless-argonaut.

JsonToClassNameMapper.scala

import scala.language.experimental.macros
import scala.reflect.macros.blackbox.Context

object JsonToClassNameMapper {

  def generatePatternMatcher[A](): (String, String) => Option[A] = macro generatePatternMatcherImpl[A]

  def generatePatternMatcherImpl[A: c.WeakTypeTag](c: Context)(): c.Tree = {
    import c.universe._
    val subclasses: Set[c.universe.Symbol] = c.weakTypeOf[A].typeSymbol.asClass.knownDirectSubclasses

    val cases = subclasses.map {
      subClass =>
        val simpleName = subClass.fullName.substring(subClass.fullName.lastIndexOf(".") + 1, subClass.fullName.length)
        cq"""$simpleName => jsonString.decodeOption[${subClass.asType}]"""
    }

    q"""(className: String, jsonString: String) =>
        className match {
          case ..$cases
        }
      """
  }
}



////TEST////


import argonaut._, Argonaut._, Shapeless._

sealed trait Foobar

case class Foo(x: Int, fooString: String) extends Foobar

import JsonToClassNameMapper._

object SealedExampleRunner extends App {

  val myJson = """{"x": 1, "fooString" :"fooString", "lanaguge" : {}}"""
  val foobarMapper = generatePatternMatcher[Foobar]()

  val result = foobarMapper("Foo", myJson)
  println("jsonToObject:" + result)

}