Scala: List[Future] to Future[List] disregarding failed futures

Question

I\'m looking for a way to convert an arbitrary length list of Futures to a Future of List. I\'m using Playframework, so ultimately, what I really want is a Future[Resu

Answer 1

I just came across this question and have another solution to offer:

def allSuccessful[A, M[X] <: TraversableOnce[X]](in: M[Future[A]])
                                                (implicit cbf: CanBuildFrom[M[Future[A]], A, M[A]], 
                                                 executor: ExecutionContext): Future[M[A]] = {
    in.foldLeft(Future.successful(cbf(in))) {
      (fr, fa) ⇒ (for (r ← fr; a ← fa) yield r += a) fallbackTo fr
    } map (_.result())
}

The idea here is that within the fold you are waiting for the next element in the list to complete (using the for-comprehension syntax) and if the next one fails you just fallback to what you already have.