Nested futures in Play for Scala does not compile

Question

This Action.async method in Play for Scala should execute the second future only if the first future returns 1, that's why they are nested. If the first future returns a result different than 1 then the second future should never be executed. But I'm getting the following compilation error in f2.map. Why is this error and how to fix it?

type mismatch; found : scala.concurrent.Future[scala.concurrent.Future[play.api.mvc.Result]] required: play.api.mvc.Result

  def index = Action.async { request =>

    val f1 =  Future {1}
    f1.map {
      access => if (access==1) {
           val f2 = Future {2} 
           f2.map {   // <-- compilation error
              result => {
                 val json = JsObject(Seq(
                      "acc" -> JsNumber(access),
                      "ret" -> JsString("0")
                  ))
                  Ok(json)
               }
          }
      }
      else {
          val json = JsObject(Seq(
              "acc" -> JsNumber(0),
              "ret" -> JsString("0")
          ))
          Future.successful(Ok(json))

      }
    }
  }

longshorej longshorej · Accepted Answer · 2016-11-24T15:42:49

You're basically there - just flatMap on f1 instead of map since you're creating another future.

Nested futures in Play for Scala does not compile

1 Answers