Spray: factor out onSuccess directive

Question

I would like to change the following code fragment in a way that I want to factor out the onSuccess block into a new method. JSON marshalling should still work.

(patch & parameterMap & asJson) { params =>
   ...
   val f:Future[ResposeData]=createResponse(...)
   onSuccess(f){complete(_)}
}

I would like to have a method like:

def handleSuccess(f:Future/FutureMagnet)(implicit ...)

A simple refactoring doesn't work for me. I tried a lot of combinations but I can't find either the correct signature or the code working.

Example:

def handleSuccess(f: Future[ResposeData]): Unit = {
    onSuccess(f) { complete(_) }
}

Error:(43, 15) type mismatch;
 found   : scala.concurrent.Future[ResponseData]
 required: spray.routing.directives.OnSuccessFutureMagnet
    onSuccess(f) {
          ^

If I now change signature I get another error:

def handleSuccess(f: OnSuccessFutureMagnet)

Error:(44, 18) spray.routing.Directive[f.Out] does not take parameters
    onSuccess(f) {
                 ^

Maybe this is just a simple thing to do but I'm new to spray. So it would be nice if somebody could give a hint.

Thanks

Answer 1

onSuccess takes a function, basically when you use that on your future the value inside the future becomes available and you can complete your route using that value if you want:

case class ResponseData(data: String)

def handleSuccess(f: Future[ResponseData]): Unit = {
  onSuccess(f) { responseData =>
    complete(_)
  }
}

From the comments:

"Unwraps" a Future[T] and runs its inner route after future completion with the future's value as an extraction of type T.

Note also that

If the future fails its failure throwable is bubbled up to the nearest ExceptionHandler.

Maybe you want to use onComplete which returns a Try and you can then match on Success or Failure.