[2.2] Coast-to-coast JSON: pickBranch with array of certain Reads?

[Jari Pennanen]

I have following code, note that "r" and "?" are just shorthands for pickBranch so the JSON code is more readable:

  

  val emptyObj = __.json.put(Json.obj())

  def ?[A <: JsValue](jspath: JsPath)(r : Reads[A]) = (jspath.json.pickBranch(r) or emptyObj)

  def r[A <: JsValue](jspath: JsPath)(r : Reads[A]) = jspath.json.pickBranch(r)

  

  val invoiceRowJson = (

    r(__ \ 'title)(Reads.of[JsString]) and

    ?(__ \ 'quantity)(Reads.of[JsNumber]) and

    ?(__ \ 'quantityUnit)(Reads.of[JsString]) and

    ?(__ \ 'price)(Reads.of[JsNumber]) and

    ?(__ \ 'tax)(Reads.of[JsNumber]) and

    ?(__ \ 'taxPrice)(Reads.of[JsNumber]) and

    ?(__ \ 'totalTaxPrice)(Reads.of[JsNumber]) and

    ?(__ \ 'totalPrice)(Reads.of[JsNumber])

  ).reduce

  

  val invoiceJson = (

    r(__ \ 'title)(Reads.of[JsString]) and

    ?(__ \ 'client)(Reads.of[JsString]) and

    ?(__ \ 'invoiceRows)(Reads.arr(invoiceRowJson)) // PSEUDO CODE "Reads.arr"

  ).reduce

See the PSEUDO code line (I've made up the Reads.arr). The problem: how can I do the reading of array of JsObjects of certain Reads?

Thanks.

- Jari

[Jari Pennanen]

Sorry, been trying to find a solution for few hours but as soon as I posted this I figured it out:

  ?(__ \ 'invoiceRows)(Reads.of[JsArray] keepAnd Reads.list(invoiceRowJson))

magical keepAnd was the answer.

[Pascal Voitot Dev]

Can you try this?

val invoiceJson = (
    r(__ \ 'title)(Reads.of[JsString]) and
    ?(__ \ 'client)(Reads.of[JsString]) and

    ?(__ \ 'invoiceRows)(Reads.list(invoiceRowJson).map(JsArray(_)))
  ).reduce

Regards
Pascal

 

Thanks.

- Jari

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[Jari Pennanen]

On Sunday, October 13, 2013 10:40:29 PM UTC+3, Pascal wrote:

Can you try this?

Hey, that works too. Thanks. 

Pascal, Do you know if it's possible to validate e.g. foreign key (which requires Future handling) in same swoop?

E.g. 

  val invoiceJson = (

    r(__ \ 'title)(of[JsString]) and

    ?(__ \ 'client)(of[JsString] keepAnd foreignkeyInCollection("client"))

  )

I can come up foreignkeyInCollection function that returns Future but I can't seem to synchronize it:

  def foreignkeyInCollection(col: String)(implicit reads: Reads[String]) =

     Reads[String](js => reads.reads(js).flatMap { id => {

      val f = db.collection[JSONCollection](col).find(Json.obj("_id" -> id))

      .cursor[JsObject].headOption.map(c => c match {

        case Some(o) =>

          o.transform(fromObjectId).map {

            js =>

              JsSuccess(js)

          } recoverTotal (e => JsError("error.foreignkey"))

        case _ => JsError("error.foreignkey")

      })

      

      // wait for F's result here somehow?

      f

     }

    }

[Pascal Voitot Dev]

Actually, you must deal with Reads[Future[JsValue]] and manage it yourself! Json transformers don't work with it!

Maybe you should do it in 2 steps... first extract the client and keep the full object... then get your data from DB and use the Future[T] to build a new Reads[Future[...]]

val invoiceJson: Reads[Future[JsValue]] = (

  (__ \ "client").read[String] and

  __.read[JsObject](yourReader)

).tupled.flatMap{ case (client, obj) =>

  foreignkeyInCollection(client).map{

    case Some(o) => Reads{ ... }

    case _ => Reads{ ... }

  }

}

If you see what I mean from these fragments :)

pascal

[Jari Pennanen]

Pascal! I got it working.

However, I know this maybe blocking the request. But does it matter if perform this only inside the Action.async?

  def foreignkeyInCollection(col: String)(implicit reads: Reads[String]) =

    Reads[JsValue](js => reads.reads(js).flatMap { id =>

      val f = db.collection[JSONCollection](col).find(Json.obj("_id" -> Json.obj("$oid" -> id)))

        .cursor[JsObject].headOption.map(c => c match {

          case Some(o) =>

            o.transform(fromObjectId).map {

              js =>

                JsSuccess(js)

            } recoverTotal (e => JsError("error.foreignkey"))

          case _ => JsError("error.foreignkey")

        })

      Await.result(f, 100 seconds)

    })

This is really amazing, the syntax for JSON developer is super clean: 

  val invoiceJson = (

    r(__ \ 'title)(of[JsString]) and

    ?(__ \ 'client)(foreignkeyInCollection("client")) and

    ?(__ \ 'address)(Client.addressJson) and

    ?(__ \ 'invoiceRows)(list(invoiceRowJson).map(JsArray(_)))).reduce