Default JsonReader of spray-json maps both JSON's null value and
no presense of object member to None.
Therefore, we cannot determine null or no presence of member if None comes
(See Sample Code!).
This library introduces an type to check member presence and
None becomes to be used only for JSON's null.
In another words, this library could be thought as a counterpart of NullOptions. NullOptions works in writing json, this library works in reading json too.
Available from maven central.
If you use SBT you can include in your project with
libraryDependencies += "com.github.bigwheel" %% "spray-json-member-presence" % "<any-version>"val nullValue = """{ "a": null }""".parseJson
val noMember = """{}""".parseJson
case class CaseClassA(a: Option[Int])
object CaseClassA extends DefaultJsonProtocol {
implicit val caseClassAFormat = jsonFormat1(CaseClassA.apply)
}
println(nullValue.convertTo[CaseClassA]) // CaseClassA(None)
println(noMember.convertTo[CaseClassA]) // CaseClassA(None)
println("Cannot distinguish 😞")
case class CaseClassB(a: MemberOption[Option[Int]])
object CaseClassB extends MemberPresenceJsonProtocol {
implicit val caseClassBFormat = jsonFormat1(CaseClassB.apply)
}
println(nullValue.convertTo[CaseClassB]) // CaseClassB(MemberSome(None))
println(noMember.convertTo[CaseClassB]) // CaseClassB(MemberNone)
println("Now we can, yeah ☺️")Complete code is Main.scala.
