In Scala Akka futures, what is the difference between map and flatMap?

Question

in normal Scala map and flatMap are different in that flatMap will return a iterable of the data flattened out into a list. However in the Akka documentation, map and flatMap se

Answer 1

I am pasting the implementation of the two methods here. the difference in english terms is below and returns the result of the function as the new future

         /** Creates a new future by applying a function to the successful result of
       *  this future. If this future is completed with an exception then the new
       *  future will also contain this exception.
       *
       *  $forComprehensionExamples
       */
      def map[S](f: T => S)(implicit executor: ExecutionContext): Future[S] = { // transform(f, identity)
        val p = Promise[S]()
        onComplete { v => p complete (v map f) }
        p.future
      }

      /** Creates a new future by applying a function to the successful result of
       *  this future, and returns the result of the function as the new future.
       *  If this future is completed with an exception then the new future will
       *  also contain this exception.
       *
       *  $forComprehensionExamples
       */
      def flatMap[S](f: T => Future[S])(implicit executor: ExecutionContext): Future[S] = {
        import impl.Promise.DefaultPromise
        val p = new DefaultPromise[S]()
        onComplete {
          case f: Failure[_] => p complete f.asInstanceOf[Failure[S]]
          case Success(v) => try f(v) match {
            // If possible, link DefaultPromises to avoid space leaks
            case dp: DefaultPromise[_] => dp.asInstanceOf[DefaultPromise[S]].linkRootOf(p)
            case fut => fut.onComplete(p.complete)(internalExecutor)
          } catch { case NonFatal(t) => p failure t }
        }
    p.future
   }

From implementation the difference is that flatMap actually calls the function with result when the promise completes.

case Success(v) => try f(v) match 

For a great article read: http//danielwestheide.com/blog/2013/01/16/the-neophytes-guide-to-scala-part-9-promises-and-futures-in-practice.html