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 stackoverflow.com/a/21469460/5160111 — Kostiantyn Palianychka
– Kostiantyn Palianychka, Commented May 31, 2017 at 8:47
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
– KimHafr, Commented May 31, 2017 at 8:55

Sam Upra · Accepted Answer · 2017-05-31 10:21:45Z

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, 2017 at 10:21

answered May 31, 2017 at 9:13

Sam Upra

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1 Comment

Stephen Over a year ago

you might like obj.zipWithIndex.map { case (itinerary, index) => ..}

chengpohi · Accepted Answer · 2017-05-31 10:16:19Z

1

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}]}}}

answered May 31, 2017 at 10:16

chengpohi

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