reactivemongo, could not find implicit value for parameter reader - scala

Question

I'm doing tests with reactivemongo
In my controller I have this:
package controllers
import models._
import models.JsonFormats._
import play.modules.reactivemongo.MongoController
import scala.concurrent.Future
import reactivemongo.api.Cursor
import org.slf4j.{LoggerFactory, Logger}
import javax.inject.Singleton
import play.api.mvc._
import reactivemongo.api.collections.default.BSONCollection
import reactivemongo.bson._
#Singleton
class Users extends Controller with MongoController {
private final val logger: Logger = LoggerFactory.getLogger(classOf[Users])
val collection = db[BSONCollection]("users")
// list all articles and sort them
def list = Action.async { implicit request =>
// get a sort document (see getSort method for more information)
val sort = getSort(request)
// build a selection document with an empty query and a sort subdocument ('$orderby')
val query = BSONDocument(
"$orderby" -> sort,
"$query" -> BSONDocument())
val activeSort = request.queryString.get("sort").flatMap(_.headOption).getOrElse("none")
// the cursor of documents
val found = collection.find(query).cursor[User]
// build (asynchronously) a list containing all the articles
found.collect[List]().map { users =>
Ok(views.html.admin.list(users, activeSort))
}.recover {
case e =>
e.printStackTrace()
BadRequest(e.getMessage())
}
}
...........
}
and in my model i have this:
package models
import reactivemongo.bson._
case class User(
nickName: String,
email: String,
password: String,
active: Boolean
)
object JsonFormats {
import play.api.libs.json.Json
// Generates Writes and Reads for Feed and User thanks to Json Macros
implicit val userFormat = Json.format[User]
}
When I compile the project returns the following error:
could not find implicit value for parameter reader: reactivemongo.bson.BSONDocumentReader[models.User]
in this line is the problem:
val found = collection.find(query).cursor[User]
Can anyone tell me where I'm wrong or what I'm missing please?

Answer 1

You have no implicit handler defined to map your model class to a BSONDocument. You can implement it yourself, or, just like you did for the JsonFormats, you could use the macros provided by ReactiveMongo.
object BsonFormats {
import reactivemongo.bson.Macros
implicit val userFormat = Macros.handler[User]
}
Alternatively, instead of the BSONCollection, you could use the JSONCollection provided by Play-ReactiveMongo to perform your mapping using the JSON format that you have already defined.

Answer 2

For me, I still get the error even after I have declared the implicits for both bson and json format. What I need to do is just import this:
import reactivemongo.api.commands.bson.BSONCountCommandImplicits._