mongodb - ReactiveMongo custom BSONDocument{ Reader, Writer } -

i'm new reactivemongo , want create custom document reader/writer 1 object i'm getting error

type mismatch;  found   : reactivemongo.bson.bsondocumentreader[reactivemongo.bson.bsondocument] required: reactivemongo.bson.bsondocumentreader[db.database.estudiante]  note: implicit object estudiantereader not applicable here because comes after application point , lacks explicit result type error occurred in application involving default arguments. 

this code , based in example found in reactivemongo's official webpage.

package db  import scala.concurrent.executioncontext.implicits.global  import reactivemongo.api._ import reactivemongo.bson._  object database {    //driver para la conexion   val driver = new mongodriver    //conexion con mongodb   val connection = driver.connection(list("localhost"))    //conexion con la base de datos amdb   val db = connection("reactive")    //colección domainnames que se encuentra en la base de datos amdb   val collection = db("estudiantes")    def findalldomainnames() = {      val query = bsondocument()     collection.find(query).cursor[estudiante]     //.cursor[bsondocument].collect[list]()   }  case class estudiante(id: option[bsonobjectid], nombre: string, apellidos: string, edad: int)    object estudiante {      implicit object estudiantewriter extends bsondocumentwriter[estudiante] {       def write(estudiante: estudiante): bsondocument = {         bsondocument(           "_id" -> estudiante.id.getorelse(bsonobjectid.generate),           "nombre" -> estudiante.nombre,           "appellidos" -> estudiante.apellidos,           "edad" -> estudiante.edad.tostring)       }     }      implicit object estudiantereader extends bsondocumentreader[estudiante] {       def read(doc: bsondocument): estudiante = {         estudiante(           doc.getas[bsonobjectid]("_id"),           doc.getas[string]("nombre").get,           doc.getas[string]("appellidos").get,           doc.getas[int]("edad").get)       }     }    }    def main(args: array[string]) {     println(findalldomainnames);   } } 

what missing/wrong?

thank in advance!

move declaration of object estudiante above database , add import in scope of database:

import estudiante._