futures

future.scala

// map creates a new future that is triggered when the originating future is done
scala> future { 42 } map { _ + 1 } map { println(_) }
43
res26: scala.concurrent.Future[Unit] = scala.concurrent.impl.Promise$DefaultPromise@5427eb13

// flatMap creates a new future that is triggered when the enclosed future is done
scala> future { 42 } flatMap { v => future { 1 + v } } map { println(_) }
res28: scala.concurrent.Future[Unit] = scala.concurrent.impl.Promise$DefaultPromise@9afcbc0

scala> 43

scala> (for { v <- future { 42 }; r <- future { 1 + v } } yield r) onSuccess { case v => println (v) }

scala> 43