Packages

object Async

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 ExecutionContext.Implicits.global
import scala.async.Async.{async, await}

def fetchURL(url: URL): Future[String] = ...

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

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("http://scala-lang.org")).length + await(fetchURL("http://docs.scala-lang.org")).length
}
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  1. final def !=(arg0: Any): Boolean
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  4. final def asInstanceOf[T0]: T0
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  5. macro def async[T](body: => T)(implicit execContext: ExecutionContext): Future[T]

    Run the block of code body asynchronously.

    Run the block of code body asynchronously. body may contain calls to await when the results of a Future are needed; this is translated into non-blocking code.

  6. def asyncImpl[T](c: Context)(body: reflect.macros.whitebox.Context.Tree)(execContext: reflect.macros.whitebox.Context.Tree)(implicit arg0: reflect.macros.whitebox.Context.WeakTypeTag[T]): reflect.macros.whitebox.Context.Tree
  7. def await[T](awaitable: Future[T]): T

    Non-blocking await the on result of awaitable.

    Non-blocking await the on result of awaitable. This may only be used directly within an enclosing async block.

    Internally, this will register the remainder of the code in enclosing async block as a callback in the onComplete handler of awaitable, and will *not* block a thread.

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    @compileTimeOnly("[async] `await` must be enclosed in an `async` block")
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