Manipulating array in JSON using Scala and JSON4S

Question

I'm trying to manipulate a JSON object in Scala using Json4s.

Say my JSON looks like this:

{
  "data": {
    "plan": {
      "itineraries": [
       {
         "startTime": 1494933289000,
         "duration": 2174
       },
       {
         "startTime": 2494933289000,
         "duration": 3174
       }
     ]
    }
  }
}

Say I want to add a field to each itinerary - Like so:

{
  "data": {
    "plan": {
      "itineraries": [
       {
         "startTime": 1494933289000,
         "duration": 2174,
         "id": "1"
       },
       {
         "startTime": 2494933289000,
         "duration": 3174,
         "id": "2"
       }
     ]
    }
  }
}

How do I do that?

maybe you can find answer in https://stackoverflow.com/a/21469460/5160111 — Kostiantyn Palianychka, May 31 '17 at 08:47
It's not the same thing :-/ I'm trying to add a unique value to each element in an array. That example is just adding a node to another node — KimHafr, May 31 '17 at 08:55

Sam Upra · Answer 1 · 2017-05-31T10:21:45.420

4

Have reader case class : ItineraryReads(startTime, duration)

Writer case class : ItineraryWrites(startTime, duration, id)

def mapToWrites(obj : List[ItineraryReads]) = {

obj.map(o => ItineraryWrites(o.startTime, o.duration, (obj.indexOf(o)) + 1))

}

This should work. Write it out as a list of ItineraryWrites :)

edited May 31 '17 at 10:21

answered May 31 '17 at 09:13

Sam Upra

737
5
12

1

you might like `obj.zipWithIndex.map { case (itinerary, index) => ..}` – Stephen May 31 '17 at 09:20

score 1 · Answer 2 · answered May 31 '17 at 10:16

transformField can be used to cover this situation with merge:

  val t = parse(s).transformField {
    case JField("itineraries", JArray(arr)) => // pattern match in there, more type safe
      val r = arr.zipWithIndex.map(f => f._1 merge JObject("id" -> JInt(f._2 + 1)))
      ("itineraries", r)
  }
  println(compact(render(t)))
  > {"data":{"plan":{"itineraries":[{"startTime":1494933289000,"duration":2174,"id":1},{"startTime":2494933289000,"duration":3174,"id":2}]}}}

Manipulating array in JSON using Scala and JSON4S

2 Answers2