JSON support for companion object

Question

I have a class that looks somewhat like that

import java.time.OffsetDateTime

import spray.json._
import DefaultJsonProtocol._

sealed trait Person {

  def firstName: String

  def country: String

  def lastName: String

  def salary: Option[BigDecimal]
}

case class InternalPerson(
                     firstName: String,
                     country: String,
                     lastName: Option[BigDecimal],
                     salary: Option[BigDecimal]
                    ) extends Person

object Person {
  def fromName(name: Name, country: String, salary: Option[BigDecimal]): Person = {
    InternalPerson(
              firstName = name.firstName,
              lastName = name.lastName,
              country = country,
              salary = salary
              )
  }
}

object PersonJsonProtocol extends DefaultJsonProtocol {
  implicit val personFormat = jsonFormat4(Person.apply)
}

I am just trying to add a json support to my class. whenever I import the protocol and spray.json._ from another classes I get:

Note: implicit value personFormat is not applicable here because it comes after the application point and it lacks an explicit result type

and

value apply is not a member of object of Person

any idea on how to have Json support for companion objects that extends a trait in scala?

Answer 1

If you defined your implicit in terms of the case class, InternalPerson, json formatting should be enabled: implicit val personFormat = jsonFormat4(InternalPerson)

And you won't have to define an apply() method, which you will have to do in either the Person trait or any implementation thereof otherwise.