ScalaJsonCombinators how to read JSON to Map[String, CaseClass] - json

Question

The JSON I need to parse is like
{
"state": "active",
"id": "11775",
"translations": {
"de_CH": {
"name": "Spiegel",
"url": "spiegel-sale"
},
"fr_CH": {
"name": "Miroirs",
"url": "promo-miroirs-femme"
}
}
In the translations, the keys de_CH and fr_CH are not known in advance. The other keys are known.
For me the translations object can be as modelled as a dictionary.
Here are the case class
case class Category(
id: String,
order: Int,
translations: Map[String, NodeTranslation]
)
case class NodeTranslation(name: String, url: String)
The ScalaJsonCombinators reads are
implicit val categoryReads = Json.format[Category
implicit val nodeTranslationReads = Json.format[NodeTranslation]]
How to read Map[String,NodeTranslation] in JSON ?
I didn't find anything for a Map there : https://www.playframework.com/documentation/2.6.x/ScalaJsonCombinators#complex-reads

Answer 1

Well that's how:
import play.api.libs.json._
import play.api.libs.functional.syntax._
case class Category(
id: String,
order: Int,
translations: Map[String, NodeTranslation]
)
case class NodeTranslation(name: String, url: String)
implicit val nodeTranslationReads = Json.format[NodeTranslation]
implicit val categoryReads: Reads[Category] = (
(__ \ 'id).read[String] and
Reads.pure[Int](123) and // your example json doesn't contain an order member so I'm not sure what you expect here
(__ \ 'translations).read[JsObject].map { obj =>
obj.value.mapValues(_.as[NodeTranslation]).toMap
}
)(Category.apply(_, _, _))
And now testing that in the repl:
val js =
"""
|{
|"state": "active",
|"id": "11775",
|"translations": {
| "de_CH": {
| "name": "Spiegel",
| "url": "spiegel-sale"
| },
| "fr_CH": {
| "name": "Miroirs",
| "url": "promo-miroirs-femme"
| }
| }
|}
""".stripMargin
val json = Json.parse(js)
json.as[Category]
the result is:
Category(11775,123,Map(de_CH -> NodeTranslation(Spiegel,spiegel-sale), fr_CH -> NodeTranslation(Miroirs,promo-miroirs-femme)))
Note that if you want to create a formatter for Category, you have to use:
(__ \ 'translations).format[JsObject].inmap(...)
nb: I really love play-json it's not always easy to use but I've yet to find a case where I can't get it to do what I need.