anuragsrivastava06

implicit def optionWriter[A]
(implicit writer: JsonWriter[A]): JsonWriter[Option[A]] =
new JsonWriter[Option[A]] {
  def write(option: Option[A]): Json =
  option match {
    case Some(aValue) => writer.write(aValue)
    case None => JsNull
  }
}

anuragsrivastava06

implicit val writer1: JsonWriter[String] = JsonWriterInstances.stringWriter

implicit val writer2: JsonWriter[String] = JsonWriterInstances.stringWriter

Json.toJson("A string")

<console>:27: error: ambiguous implicit values:
 both value stringWriter in object JsonWriterInstances of type => JsonWriter[String]
 and value writer1 of type => JsonWriter[String]
 match expected type JsonWriter[String]

anuragsrivastava06

import JsonWriterInstances._
import JsonSyntax._
Person("Dave", "dave@example.com").toJson

// res6: Json = JsObject(Map(name -> JsString(Dave), email -> JsString(dave@example.com)))

anuragsrivastava06

object JsonSyntax {
	implicit class JsonWriterOps[A](value: A) {
		def toJson(implicit w: JsonWriter[A]): Json =
		w.write(value)
	}
}

anuragsrivastava06

import JsonWriterInstances._

Json.toJson(Person("Dave", "dave@example.com"))

//res1: Json = JsObject(Map(name -> JsString(Dave), email -> JsString(dave@example.com)))

anuragsrivastava06

object Json {
  def toJson[A](value: A)(implicit w: JsonWriter[A]): Json = w.write(value)
}

anuragsrivastava06

final case class Person(name: String, email: String)

object JsonWriterInstances {
  implicit val stringWriter: JsonWriter[String] =
  new JsonWriter[String] {
    def write(value: String): Json = JsString(value)
  }

  implicit val personWriter: JsonWriter[Person] =
  new JsonWriter[Person] {

anuragsrivastava06

sealed trait Json 

final case class JsObject(get: Map[String, Json]) extends Json

final case class JsString(get: String) extends Json

final case class JsNumber(get: Double) extends Json

case object JsNull extends Json