I am writing a JSON Writes. In models/Users.scala, I have defined an implicit object with implicit definitions.
object UserImplicits {
/*Writes (write to JsValue) are used by toJson method of Json object to convert data (say the model) to JsValue*/
implicit val profileWrites:Writes[UserProfile] = (
(JsPath \ "confirmed").write[Boolean] and
(JsPath \ "email").write[String] and
(JsPath \ "firstname").write[String] and
(JsPath \ "lastname").write[String]
) (unlift(UserProfile.unapply))
implicit val userWrites: Writes[User] = (
(JsPath \ "id").write[UUID] and
(JsPath \ "user-profile").write[UserProfile]
) (unlift(User.unapply))
implicit val usersResourceWrites:Writes[UsersResource] = (
(JsPath \ "id").write[String] and
(JsPath \ "url").write[String] and
(JsPath \ "user").write[User]
) (unlift(UsersResource.unapply))
/*Reads (read from JsValue) is used by Json object's as or asOpt methods to convert JsValue to some other data, eg your model*/
implicit val profileReads:Reads[UserProfile] = (
(JsPath \ "confirmed").read[Boolean] and
(JsPath \ "email").read[String] and
(JsPath \ "firstname").read[String] and
(JsPath \ "lastname").read[String]
) (UserProfile.apply _)
implicit val userReads: Reads[User] = (
(JsPath \ "id").read[UUID] and
(JsPath \ "user-profile").read[UserProfile]
) (User.apply _)
implicit val usersResourceReads: Reads[UsersResource] = (
(JsPath \ "id").read[String] and
(JsPath \ "url").read[String] and
(JsPath \ "user").read[User]
) (UsersResource.apply _)
}
In my controller class, I have imported models._ and have defined the controller as follows:
import models._
import scala.concurrent.{ExecutionContext, Future}
class UserController @Inject()(cc: ControllerComponents)(implicit exec: ExecutionContext) extends AbstractController(cc){
//TODOM - remove hard coded response
def addUser = Action.async{ implicit request => {
println("addUser controller called")
val user = User(UUID.randomUUID(),UserProfile(true,"m@m.com","m","c"))
val userResource = UsersResource(user.id.toString(),"/ws/users",user)
val json = Json.toJson(userResource); //converts the model to JsValue using Writes defined in Users model class
println("returning json:",Json.prettyPrint(json))
Future{Ok(json)}}
}
I am getting the following compilation error.
No Json serializer found for type models.UsersResource. Try to implement an implicit Writes or Format for this type. for code val json = Json.toJson(userResource);
The issue seem to be Play cannot find the implicit Writes. The code works if I move the implicit definitions in controller instead of defining in models. How could I make the implicits defined in model/user.scala visible in the controller class?
I had to create another object (not companion object) and add the implicit definitions there.
to use these implicits, use import models.UserImplicits._ in files where implicits are required.
object UserImplicits {
/*Writes (write to JsValue) are used by toJson method of Json object to convert data (say the model) to JsValue*/
implicit val profileWrites:Writes[UserProfile] = (
(JsPath \ "confirmed").write[Boolean] and
(JsPath \ "email").writeNullable[String] and
(JsPath \ "firstname").writeNullable[String] and
(JsPath \ "lastname").writeNullable[String]
) (unlift(UserProfile.unapply))
implicit val userWrites: Writes[User] = (
(JsPath \ "id").write[UUID] and
(JsPath \ "user-profile").write[UserProfile]
) (unlift(User.unapply))
implicit val usersResourceWrites:Writes[UsersResource] = (
(JsPath \ "id").write[String] and
(JsPath \ "url").write[String] and
(JsPath \ "user").write[User]
) (unlift(UsersResource.unapply))
/*Reads (read from JsValue) is used by Json object's as or asOpt methods to convert JsValue to some other data, eg your model*/
implicit val profileReads:Reads[UserProfile] = (
(JsPath \ "confirmed").read[Boolean] and
(JsPath \ "email").readNullable[String] and
(JsPath \ "firstname").readNullable[String] and
(JsPath \ "lastname").readNullable[String]
) (UserProfile.apply _)
implicit val userReads: Reads[User] = (
(JsPath \ "id").read[UUID] and
(JsPath \ "user-profile").read[UserProfile]
) (User.apply _)
implicit val usersResourceReads: Reads[UsersResource] = (
(JsPath \ "id").read[String] and
(JsPath \ "url").read[String] and
(JsPath \ "user").read[User]
) (UsersResource.apply _)
}