Scala Play framework 'update' json array

Question

Suppose I have a json array that looks like this (I receive it from a remote service):

[{"id": 1}, {"id": 2}, ... , {"id": 10}]

And, say, I want to 'transform' it like this (add 100 to 'id's and other values):

[{"id": 101}, {"id": 102}, ..., {"id": 110} ]

As for starters I wanted to 'update' it so that it would at least replace the initial array with a blank one (just to test how stuff works).

Json.parse("""[{"id": 1}, {"id": 2}]""").transform( (__).json.update( __.read[JsArray].map(_ => JsArray()) ))

But it throws an exception:

play.api.libs.json.JsResult[play.api.libs.json.JsObject] = JsError(List((,List(ValidationError(List(error.expected.jsobject),WrappedArray())))))

However if they are sealed inside of a json object then it kinda works:

Json.parse("""{"ids": [{"id": 1}, {"id": 2}]}""").transform( (__ \ "ids").json.update( __.read[JsArray].map(_ => JsArray()) ))

which results in

play.api.libs.json.JsResult[play.api.libs.json.JsObject] = JsSuccess({"ids":[]},/ids)

How do I deal with array json? Thanks in advance

Johny T Koshy · Accepted Answer · 2015-12-03 16:46:31Z

4

Try the following code,

case class ID(id: Int)
implicit val reads = Json.reads[ID]

Json.parse("""[{"id": 1}, {"id": 2}]""").as[JsArray].value.map(_.transform(__.json.update {
  __.read[ID].map { case x: ID => Json.obj("id" -> (x.id + 100)) }
}))

answered Dec 3, 2015 at 16:46

Johny T Koshy

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3 Comments

Dmitri Over a year ago

Thanks! But what if I want to output it to the user's browser? It seems that I cannot just pass it to "Ok(...)" as it is not "Writable".

Johny T Koshy Over a year ago

Why not ask this as a separate question?

Dmitri Over a year ago

Seems reasonable! Thank you for your help.

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