Example on how to execute scala futures in serial one after the other, without collecting the result of the futures

ExampleExecuteScalaFuturesInSerial.scala

/*
Example on how to execute scala futures in serial one after the other, without collecting the result of the futures

Look this instead if we need to collect the result of the futures (it also explains how foldLeft works here):
https://gist.github.com/dportabella/4e7569643ad693433ec6b86968f589b8
*/


import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration.Duration
import scala.concurrent.{Await, ExecutionContext, Future}

object ExampleExecuteScalaFuturesInSerial extends App {
  def myFuture(i: Int) = Future {
    Thread.sleep(1000)
    val s = s"done: $i"
    println(s)
  }

  def serialiseFutures[A](list: Iterable[A])(fn: A => Future[Unit])(implicit ec: ExecutionContext): Future[Unit] = {
    val zero = Future(())
    list.foldLeft(zero) { (accFuture, nextItem) =>
      accFuture.flatMap(_ => {
        val nextFuture = fn(nextItem)
        nextFuture
      })
    }
  }

  def task = serialiseFutures(List(10, 20, 30)) { i => myFuture(i) }

  Await.result(task, Duration.Inf)
}