Decoding a Seq of objects using Circe

Question

I have two classes that look something like that

import io.circe.Decoder

case class FactResponse(id: String, status: String) {
  ...
}


object FactResponse {

  implicit val decoder: Decoder[FactResponse] =
    Decoder.forProduct2("id", "status")(FactResponse.apply)

  def apply(json: String): FactResponse = {
    import io.circe.parser.decode
    decode[FactResponse](json).right.get
  }
}    



case class RuleEngineRequestResponse(content: Seq[Map[String, String]])

object RuleEngineRequestResponse {

  implicit val decoder: Decoder[RuleEngineRequestResponse] =
    Decoder.forProduct1("content")(RuleEngineRequestResponse.apply(_: String))

  def apply(json: String): RuleEngineRequestResponse = {
    import io.circe.parser.decode
    println("here")
    print(json)
    println(decode[RuleEngineRequestResponse](json).left.get)
    decode[RuleEngineRequestResponse](json).right.get
  }
}

I am trying to decode a json that looks something like this

{ "content" :[{"id":"22", "status":"22"]}

However, I am getting a decoding failure DecodingFailure(String, downfield("content"))

I am not really sure what is going wrong here, the json is definitely a correct one, I even tried to parse the content into a sequence of maps but still, I get the same thing over and over again. any idea on how to parse nested objects as an array using circe?

Answer 1

I think you can simplify the decoding a lot if you let circe derive the decoders automatically:

import io.circe.generic.auto._
import io.circe.parser.decode

case class FactResponse(id: String, status: String)
case class RuleEngineRequestResponse(content: Seq[FactResponse])

object Sample extends App {
  val testData1 =
    """
      |{
      |   "content":[
      |      {
      |         "id":"22",
      |         "status":"22"
      |      }
      |   ]
      |}""".stripMargin

  val testData2 =
    """
      |{
      |   "content":[
      |      {
      |         "id":"22",
      |         "status":"22"
      |      },
      |      {
      |         "id":"45",
      |         "status":"56"
      |      }
      |   ]
      |}""".stripMargin

  println(decode[RuleEngineRequestResponse](testData1))
  println(decode[RuleEngineRequestResponse](testData2))

}

This outputs:

Right(RuleEngineRequestResponse(List(FactResponse(22,22))))
Right(RuleEngineRequestResponse(List(FactResponse(22,22), FactResponse(45,56))))

You will need to include dependencies:

  "io.circe" %% "circe-generic" % circeVersion,
  "io.circe" %% "circe-parser"  % circeVersion,

I used circe version 0.10.0

You can check it out here.