CODEWITHSUNDEEP
scalaasynchronous
joesan
joesan

Reputation: 15345

Scala async Behavior

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?

Upvotes: 0

Views: 89

Answers (1)

bjfletcher
bjfletcher

Reputation: 11498

It depends what you meant by "waits", what happens is that, unlike with Scala's ordinary Await.result which blocks the thread, await wraps the rest of the code as a Future, and frees up the thread to continue running outside the async block.

Upvotes: 1

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