decorator.scala

trait Decorable[A, B] {
  def decorate(obj: A, dec: B): Either[String, A]
}

object Decorator {
  def decorate[A, B](implicit d: Decorable[A,B]) = d
}

object TagsDecorator {

  implicit object DecorableClick extends Decorable[Click, TagsDecorator] {
    override def decorate(obj: Click, dec: TagsDecorator) = {
      Try(Right(obj.copy(tags = dec.getTagsForCid(obj.dst_cid)))).recover { 
        case e: Throwable => Left(e.getMessage)
      }.get
    }
  }

}



class TagsDecorator extends Decorator {

  def getTagsForCid(cid: Long): List[String] = {
    List("f")
  }

}

case class A {}


object Main {

  val b: TagsDecorator = new TagsDecorator

  import TagsDecorator._


}