Scala async Behavior

Question

In the following sample method implementation that uses the Scala async:

  def doSomething: Future[Int] = async {
    val await1 = await(someFutureResult1()) // Line 1

    val await2 = await(someFutureResult2()) // Line 2

    val syncCall = someFunc3() // Line 3

    await1 + await2 + syncCall // Line 4
  }

How is the ordering happening? The caller of doSomething returns immediately because the doSomething() is going to run in an async block. I get that. But what happens when some other thread picks up this execution and executes the contents of doSomething?

My understanding is as follows:

Line 1 starts and waits until the Future returned by someFutureResult1() is completed. Line 2 and Line 3 is not yet started!

Line 2 starts and waits until the Future returned by someFutureResult2() is completed

Line 3 starts and returns

Line 4 is called and returned

Is the flow correct?

Answer 1

它取决于您的“等待”的意思，发生的情况是，与Scala的普通Await.result不同，它阻塞线程， await将其余代码包装为Future ，并释放线程以继续在async块外运行。