CodecJson.xmap

gistfile1.scala

case class Username(value: String)

implicit val usernameCodec = implicitly[CodecJson[String]].xmap(Username.apply)(_.value)

// ------------------------------------------------------------------------------------------------
// Would like to eventually like to do something like this:
// (Basically a replacement the {@@, T with U} hack which has caused me too many problems)

trait TaggedType { type U; def value: U }                                                                                
trait TaggedTypeCtor[T <: TaggedType] { def apply(u: T#U): T }

implicit def codecTagged[T <: TaggedType](implicit TC: TaggedTypeCtor[T], c: CodecJson[T#U]): CodecJson[T] =
  c.xmap(TC.apply)(_.value)