Extract fields from JsArray in scala on play framework

Question

I have a JSArray like below from server (I cannot change as it belongs to others):

[ {"name": "US", "id": 0, "translations" : {"name: {"es": "Estados unidos", "fr": "Etats-unis"}}},
{"name": "UK", "id": 1, "translations" : {"name: {"es": "Estados Kdda", "fr": "dsfjas"}}},
...
]

I need to extract all the name like US, UK but not name in translations and also id.

I tried several ways and it always have problem. Below are what I tried.

I first tried

case class Country(name: String, id:String) 

implicit object CountryReads extends Reads[Country] {  
def reads(json: JsValue) = Country(
                        (json \ "name"),
                        (json \ "id")
                    )
}

val countries = Json.parse(result) match {  //here result is Json String
           case JsArray(Seq(t)) => Some(t.as[Seq[Country]])
           case _ => None
}

But I get compiling error as below:

[error] C:\git9\hss\app\models\LivingSocial.scala:80: type mismatch;
[error]  found   : play.api.libs.json.JsValue
[error]  required: play.api.libs.json.JsResult[MyCountry]
[error]                        def reads(json: JsValue) =    (json \ "currencyCode")
[error]                                                            ^
[error] one error found
[error] (compile:compile) Compilation failed

then I tried:

val jResult = Json.parse(result)
(jResult \\ "name").foreach { name => 
   println(name.as[String])
}

I get error in println() as "\" will recursively pull names under translation also.

Any good way to do it?

Your compiler error references a currencyCode field which isn't in your code. Are you sure that's everything? — Ryan
– Ryan, Commented Aug 14, 2014 at 22:11

Ryan · Accepted Answer · 2014-08-14 22:16:11Z

2

case class Country(name: String, id: Int, translations: Map[String, Map[String, String]])

object Country {

  implicit val format = Json.format[Country]

}

val js = Json.parse(yourString)

val names: JsResult[Seq[String]] = js.validate[Seq[Country]].map { countries => countries.map(_.name) }

At that point you can deal with the JsResult since you'll need error handling in case the JSON doesn't conform to your expectations.

answered Aug 14, 2014 at 22:16

Ryan

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Comments

faissalb · Accepted Answer · 2014-08-15 01:21:29Z

0

You can change your read to look like this :

implicit val CountryReads: Reads[Country] = (
        (JsPath \ "name").read[String] and
          (JsPath \ "name").read[String]
        )(Country.apply _)

this is a correct way to create a reader according to play documentation

edited Aug 15, 2014 at 1:21

answered Aug 14, 2014 at 22:15

faissalb

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1 Comment

drstevens Over a year ago

There is no one right way to create a reader according to the pre-canned Reads definitions in the play source - github.com/playframework/playframework/blob/master/framework/…

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