Qfyilyi

I have the following Json block that I have returned as a JsObject

{

  "first_block": [

    {

      "name": "demo",

      "description": "first demo description"

    }

  ],

  "second_block": [

    {

      "name": "second_demo",

      "description": "second demo description",

      "nested_second": [

        {

          "name": "bob",

          "value": null

        },

        {

          "name": "john",

          "value": null

        }

      ]

    }

  ]

}

From this, I want to return a list of all the possible values I could have in the second block, nested array for name and value. so with the example above
List([bob,null],[john,null]) or something along those lines.

The issue I am having is with the value section understanding null values. I've tried to match against it and return a string "null" but I can't get it to match on Null values.

What would be the best way for me to return back the name and values in the nested_second array.

I've tried using case classes and readAsNullable with no luck, and my latest attempt has gone along these lines:

val secondBlock = (jsObj  "second_block").as[List[JsValue]]



secondBlock.foreach(nested_block => {

  val nestedBlock = (nested_block  "nested_second").as[List[JsValue]]

  nestedBlock.foreach(value => {

    val name = (value  "name").as[String] //always a string

    var convertedValue = ""

    val replacement_value = value  "value"

    replacement_value match {

      case JsDefined(null) => convertedValue = "null"

      case _ => convertedValue = replacement_value.as[String]

    }



    println(name)

    println(convertedValue)

  })

}

)

It seems convertedValue returns as 'JsDefined(null)' regardless and I'm sure the way I'm doing it is horrifically bad.

Replace JsDefined(null) with JsDefined(JsNull).

You probably got confused, because println(JsDefined(JsNull)) prints as JsDefined(null). But that is not, how null value of a JSON field is represented. null is represented as case object JsNull. This is just a good API design, where possible cases are represented with a hierarchy of classes:

With play-json I use always case-classes!

I simplified your problem to the essence:

import play.api.libs.json._



val jsonStr = """[

        {

          "name": "bob",

          "value": null

        },

        {

          "name": "john",

          "value": "aValue"

        },

        {

          "name": "john",

          "value": null

        }

      ]"""

Define a case class

case class Element(name: String, value: Option[String])

Add a formatter in the companion object:

object Element {

  implicit val jsonFormat: Format[Element] = Json.format[Element]

}

An use validate:

Json.parse(jsonStr).validate[Seq[Element]] match {

  case JsSuccess(elems, _) => println(elems)

  case other => println(s"Handle exception $other")

}

This returns: List(Element(bob,None), Element(john,Some(aValue)), Element(john,None))

Now you can do whatever you want with the values.