Scala return result from a Promise

Question

Looking to achieve this:

HTTP request to REST API -> parse -> make async call to another API -> respond to http req with the result of the async call.

Currently, the code looks like:

 def getItems(param: String): LiftResponse = {

    @volatile var resp: LiftResponse = new BadResponse

    param.toLowerCase match {
      case "something" =>
        val req = Async call returning a Future
        req onSuccess {
          case items =>
            resp = new JsonResponse(items map (decompose(_)), S.getResponseHeaders(Nil), S.responseCookies, 200)
        }
        req onFailure {
          case fail => resp = new BadResponse
        }
        resp

      case _ => new OkResponse
    }
  }

But it looks like poor implementation.

What is the idiomatic Scala way to write the above?

Answer 1

I think you can try to inline @volatile var resp by:

def getItems(param: String): LiftResponse = {

    param.toLowerCase match {
        case "something" =>
            val req = Async call returning a Future
            req.onComplete {
                case Success(items) => new JsonResponse(items map (decompose(_)), S.getResponseHeaders(Nil), S.responseCookies, 200)
                case Failure(t) => new BadResponse
            }
        case _ => new OkResponse
    }

}

--edit--

sorry, onComplete returns Unit, how about using Await to get the result of future:

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent._
import scala.concurrent.duration._

def getItems(param: String): LiftResponse = {

    param.toLowerCase match {
        case "something" =>
            val req = Async call returning a Future
            val response = req map { items => 
                new JsonResponse 
            } recover { 
                case t:Throwable => new BadResponse
            }
            Await.result(response, Duration(100, MILLISECONDS))
        case _ => new OkResponse
    }

}