PlayJson Example of how to use a strongly typed string via case class, yet not change json

output.txt

{"name":"dino","myAddress":"some place"}
Person(dino,Address(some place))
Person(John,Address(London))
Address(London)
London
Map(Address(place a) -> KT18 7LY, Address(place b) -> BN26 5HQ)
{"place a":"KT18 7LY","place b":"BN26 5HQ"}

// without keyReads/Writes you would get this on the last line

[["place a","KT18 7LY"],["place b","BN26 5HQ"]]

PlayJsonAnyVal.scala

import play.api.libs.json._

object PlayJsonAnyVal extends App {

  final case class Address(path: String) extends AnyVal

  object Address {
    // this allows Address to be used as a map key, even though it is not a String
   implicit val keyReads: KeyReads[Address]= key => JsSuccess(Address(key))
   implicit val keyWrites: KeyWrites[Address] = _.path
   
    implicit val addressFormat: Format[Address] = Json.valueFormat[Address]
  }

  case class Person(name: String, myAddress: Address)

  object Person {
    implicit val format: Format[Person] = Json.format[Person]
  }

  val dino = Person("dino", Address("some place"))

  val out: JsValue = Json.toJson(dino)

  // note, no mention of path in the json or "Address"

  println(out)

  val dinoin: Person = out.as[Person]

  println(dinoin)

  val john=Json.parse("""{"name":"John","myAddress":"London"}""").as[Person]
  println(john)
  println(john.myAddress)
  println(john.myAddress.path)
  
  val addressPostCode=Map[Address,String](Address("place a")-> "KT18 7LY", Address("place b")->"BN26 5HQ")
  
  println(addressPostCode)
  
  println(Json.toJson(addressPostCode))
}