Magnet pattern

gistfile1.txt

// Problem: type erasure
def complete[T :Marshaller](status: StatusCode, obj: T): Unit
def complete(future: Future[HttpResponse]): Int
def complete(future: Future[StatusCode]): Int

// Usage of CompletionMagnet
def complete(magnet: CompletionMagnet): magnet.Result = magnet()

sealed trait CompletionMagnet {
  type Result
  def apply(): Result
}

object CompletionMagnet {
  implicit def fromStatusObject[T :Marshaller](tuple: (StatusCode, T)) =
    new CompletionMagnet {
      type Result = Unit
      def apply(): Result = ... // implementation using (StatusCode, T) tuple
    }
  implicit def fromHttpResponseFuture(future: Future[HttpResponse]) =
    new CompletionMagnet {
      type Result = Int
      def apply(): Result = ... // implementation using future
    }
  implicit def fromStatusCodeFuture(future: Future[StatusCode]) =
    new CompletionMagnet {
      type Result = Int
      def apply(): Result = ... // implementation using future
    }
}