scala.async

Type members

Classlikes

Async blocks provide a direct means to work with scala.concurrent.Future.

For example, to use an API that fetches a web page to fetch two pages and add their lengths:

import scala.concurrent._, duration._
import akka.util._, akka.actor._, akka.http.scaladsl._, model._
import scala.async.Async.{async, await}
implicit val system = ActorSystem()
import system.dispatcher
def fetchURL(url: Uri): Future[ByteString] = async {
 val response = await(Http().singleRequest(HttpRequest(HttpMethods.GET, url)))
 val entity = await(response.entity.toStrict(5.seconds))
 entity.data
}

Example:

val sumLengths: Future[Int] = async {
 val body1 = fetchURL("https://scala-lang.org")
 val body2 = fetchURL("https://docs.scala-lang.org")
 await(body1).length + await(body2).length
}
async {
 await(sumLengths) should be > 50000
}

Note that in the following program, the second fetch does not start until after the first. If you need to start tasks in parallel, you must do so before await-ing a result.

val sumLengths: Future[Int] = async {
 await(fetchURL("https://scala-lang.org")).length + await(fetchURL("https://docs.scala-lang.org")).length
}
async {
 await(sumLengths) should be > 50000
}