CODEWITHSUNDEEP
jsonscalacirce
Knows Not Much
Knows Not Much

Reputation: 31546

Parse Json using Circe and monocle lens

I have written this sample code

package com.abhi
import io.circe._
import io.circe.optics.JsonPath._

object CirceTest extends App {
   val id = root.id.long
   val date = root.date.long

   val input =
      """
        |{
        |  "id" : 0,
        |  "childIds" : [
        |    11, 12, 13
        |  ],
        |  "date" : 1480815583505
        |}
      """.stripMargin
   parser.parse(input) match {
      case Left(a) => println(s"failed ${a}")
      case Right(json) =>
         val myId = id.getOption(json).get
         val myDate = date.getOption(json).get
         println(s"id: ${myId} date: ${myDate}")
   }
}

but this won't event compile

CirceTest.scala:26: constructor cannot be instantiated to expected type;
[error]  found   : scala.util.Right[A,B]
[error]  required: cats.data.Xor[io.circe.ParsingFailure,io.circe.Json]
[error]       case Right(json) =>
[error]            ^

I also tried

val jsonEither = parser.parse(input)
if (jsonEither.isRight) {
   val json = jsonEither.right.get
   val myId = id.getOption(json).get
   val myDate = date.getOption(json).get
   println(s"id: ${myId} date: ${myDate}")
}

but this also fails

[error] CirceTest.scala:27: value right is not a member of cats.data.Xor[io.circe.ParsingFailure,io.circe.Json]
[error]       val json = jsonEither.right.get
[error]                             ^
[error] one error found

I am pretty surprised. when I can do a isRight then why does compiler say that I can't do a right?

Here is my build.sbt file

name := "CirceTest"

version := "1.0"

scalaVersion := "2.11.8"

libraryDependencies ++= Seq(
   "io.circe" %% "circe-core" % "0.5.1",
   "io.circe" %% "circe-generic" % "0.5.1",
   "io.circe" %% "circe-parser" % "0.5.1",
   "io.circe" %% "circe-optics" % "0.5.1"
)

Upvotes: 1

Views: 1036

Answers (1)

Travis Brown
Travis Brown

Reputation: 139038

Circe depends on the Cats library, which recently removed cats.data.Xor, which was a right-biased Either-like type. Circe 0.5.0 and earlier versions used cats.data.Xor as the result type for parsing and decoding, but 0.6.0+ use the standard library's Either, since Xor is gone.

Updating your circe dependency to 0.6.1 will make your code work as written. If for some reason you're stuck on an earlier version of circe, you'll need to adjust your code to work with Xor. I'd suggest sticking to the most recent version, though—both circe and Cats are young projects and things are moving quickly. If you are stuck on an earlier version, and it's because of a library that depends on circe, please get in touch on Gitter and we'll try to work with the library maintainers to get things updated.

Upvotes: 3

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