Scala implicit converters - scala

Question

I'm trying to figure out how to create an implicit converter for a particular type. In my case, that would be a Set[IdParam[T]] to a Set[IdTag[T]], where
import shapeless.tag.##
case class IdParam[T](value: IdTag[T])
type IdTag[T] = Id ## T
class Id(val value: Long)
object Id {
def tag[T](l: Long) = shapeless.tag[T][Id](new Id(l))
def value[T](l: Long) = Id.tag[T](l)
}
I wrote a simple
implicit def toIds[T](idParams: Set[IdParam[T]]): Set[IdTag[T]] = idParams.map(_.value)
which works OK. But my main question now is if there is a way to create an implicit converter which would cover both Seq and Set. Going up the hierarchy, that would mean an Iterable.
Tried the following
implicit def toIds[I <: Iterable[IdParam[T]], T](idParams: I): Iterable[IdTag[T]] = idParams.map(_.value)
The compiler refuses to accept this converter where it's needed.
[error] found : Set[tags.IdParam[tags.ProfileIdTag]]
[error] required: Set[tags.ProfileId]
[error] (which expands to) Set[model.Id with shapeless.tag.Tagged[tags.ProfileIdTag]]
EDIT
That implicit converter should be used in the Controller endpoint.
GET /campaigns #dummy.Campaigns.all(profileId: Set[IdParam[ProfileIdTag]] ?= Set.empty)
I have a QueryStringBindable which converts the query param retrieved as a string into a Set[IdParam[A]]
object IdQueryStringBinder {
implicit def idParamQueryStringBinder[A](implicit stringBinder: QueryStringBindable[String]) =
new QueryStringBindable[IdParam[A]] {
def bind(key: String, params: Map[String, Seq[String]]): Option[Either[String, IdParam[A]]] =
for {
idEither <- stringBinder.bind(key, params)
} yield {
idEither match {
case Right(idString) =>
IdBinder.parseIdString(idString)
case Left(_) => Left("Unable to bind an Id")
}
}
override def unbind(key: String, id: IdParam[A]): String =
stringBinder.unbind(key, id.value.toString)
}
implicit def idsParamQueryStringBinder[A](implicit stringBinder: QueryStringBindable[String]) =
new QueryStringBindable[Set[IdParam[A]]] {
override def bind(key: String, params: Map[String, Seq[String]]): Option[Either[String, Set[IdParam[A]]]] = {
stringBinder.bind(key, params).map(_.right.flatMap(parse))
}
private def parse(idsString: String): Either[String, Set[IdParam[A]]] = {
val (wrongIds, correctIds) = idsString.split(",")
.map(id => IdBinder.parseIdString[A](id))
.partition(_.isLeft)
if (wrongIds.nonEmpty) {
Left(s"Could not bind the following Ids: ${wrongIds.map(_.left.get).mkString(",")}")
} else {
Right(correctIds.map(_.right.get).toSet)
}
}
override def unbind(key: String, ids: Set[IdParam[A]]): String =
stringBinder.unbind(key, ids.map(_.value.toString).mkString(","))
}
}
My Controller is
class Campaigns extends play.api.mvc.Controller {
def allByProfileId(profile: ProfileId) = ...
def all(profileIds: Set[ProfileId]) = ...
}
The first endpoint works, which uses the defined idParamQueryStringBinder with the following implicit converter
implicit def toId[T](idParam: IdParam[T]): IdTag[T] = idParam.value

Answer 1

You must have done some coding mistake because it works perfectly fine for me:
https://gist.github.com/kpbochenek/ce2a783d59a7bd28585e4cbf7a64cad4
next time paste full code that causes the issue not only small parts.