Play2 does not find my implicit Reads or Format for JSON

Question

This is my Search Object: ``` package models.helper import play.api.libs.json.Format import play.api.libs.json.JsValue import play.api.libs.json.JsObject import play.api.libs.json.JsString case class Search (name: String, `type`:String){ implicit object SearchFormat extends Format[Search] { def reads(json: JsValue): Search = Search( (json \ "name").as[String], (json \ "type").as[String] ) def writes(s: Search): JsValue = JsObject(Seq( "name" -> JsString(s.name), "type" -> JsString(s.`type`) )) } } ``` I'm trying ot use this class when calling a webservice using WS: ``` val search = response.json.as[Search] ``` But the scala compiler keeps complaining on this line: No Json deserializer found for type models.helper.Search. Try to implement an implicit Reads or Format for this type. Could anybody tell me what I'm doing wrong? - got the example from https://sites.google.com/site/play20zh/scala-developers/working-with-json - this thread discusses the same issue but gives no solution, what…

Accepted Answer

Indeed the example is wrong. You need your implicit `Format[Search]` value to be available in the implicit scope.

In your case the `Format[Search]` is defined as a nested value of the class `Search`, so you can reach it only from an instance of `Search`.

So, what you want to do is to define it in another place, where it could be referenced without having to create an instance of `Search`, e.g. in a `Formats` object:

```
object Formats {
  implicit SearchFormat extends Format[Search] {
    …
  }
}
```

Then you can use it as follows:

```
import Formats.SearchFormat
val search = response.json.as[Search]
```

You can also get rid of the import tax by defining the `Format[Search]` value in the companion object of the `Search` class. Indeed the Scala compiler automatically looks in companion objects of type parameters when it needs an implicit value of a given type:

```
case class Search(name: String, `type`: String)

object Search {
  implicit object SearchFormat extends Format[Search] {
    …
  }
}
```

Then you can use it without having to import it:

```
val search = response.json.as[Search]
```

Play2 does not find my implicit Reads or Format for JSON

Solution

Problem