How to use Circe Optics and Decode together - scala

Question

I am using circe optics like this
import io.circe.parser._
import io.circe.optics._
import io.circe.optics.JsonPath._
val json = parse("""{"response": {"person": {"firstname": "foo", "lastname":"bar"}}}""").right.get
Now I want to extract the whole person object in string form ... from this json like
val p = root.response.person.string
and then decode it into a case class like
case class Person(firstname: String, lastname: String)
decode[Person](p.getOption(json).get)
But it doesn't work because root.response.person.string returns null. I think it only works on actual string and integer columns.
So can circe optics be used to extract entire sections of json (for example the person object inside of json)? and then that section is decoded into a case class?

Answer 1

This gets it done. No need to get the string in between, just work with the Json
object Some extends App {
import io.circe.optics.JsonPath._
import io.circe.parser._
import io.circe._
import io.circe.generic.semiauto._
val json = parse("""{"response": {"person": {"firstname": "foo", "lastname":"bar"}}}""").right.get
// this is just a lense to the person, not the person yet
val personJsonPath = root.response.person.json
case class Person(firstname: String, lastname: String)
implicit val personDecoder: Decoder[Person] = deriveDecoder[Person]
val maybePerson = personJsonPath
// here you get the person out
.getOption(json)
// transforming json directly to case class, error handling should not be done like this ;)
.map(_.as[Person].fold(throw _, identity))
println(maybePerson)
}