Scala:Futures vs Promises

A code snippet that uses both Promise and Future

PS:the code is a part of AsyncController in the play-scala-starter-example

  private def getFutureMessage(delayTime: FiniteDuration): Future[String] = {
    val promise: Promise[String] = Promise[String]()
    actorSystem.scheduler.scheduleOnce(delayTime) {
    }(actorSystem.dispatcher) // run scheduled tasks using the actor system's dispatcher

What’s the difference between Futures and Promises

Aleksandar gave a great explanation here,to make it short.

1.You can think of futures and promises as two different sides of a pipe. On the promise side, data is pushed in, and on the future side, data can be pulled out.

2.To divide promises and futures into 2 separate interfaces was a design decision

3.By returning a promise you are giving the right to complete it to somebody else, and by returning the future you are giving the right to subscribe to it.