Using For Comprehension for async callbacks?

[Vincent Marquez]

Hello everyone, 

I've written SIP server and library in Scala and like in any network/server type code, in a lot of places i'm having to write nested callbacks which can look quite ugly: 

obj.connect( "some parameters", ()=> 

    obj2.connect("more parameters"), ()=>
         obj3.connect("even more"), ()=> 

               println("everone connceted"))))

so it occurred to me I could (arguably) make it a bit neater by using for comprehension.  Then it occurred to me there may already be an idiomatic "scala" way of doing this, and I shouldn't reinvent the wheel if so.   

Here's what I whipped up as an example of the kind of thing I want to do.  Obviously, instead of a sleep I'd be actually sending the whole method off to an actor which would do some stuff, and the callback would occur in another thread... 

http://pastebin.com/4Vy2SKmH

Too much abstraction?  Beautiful code?  Akka already has this? :-)  Thanks in advance!

--Vincent

[Vlad Patryshev]

Goo idea. I believe this is how it should be.

-Vlad

[√iktor Ҡlang]

import akka.dispatch._

import akka.dispatch.Future._

val result = flow {

  val f1: Future[Long] = someCalcReturningFuture

  val f2: Future[Long] = someOtherCalcReturningFuture

  f1() + f2()

}

or

val f1: Future[Long] = someCalcReturningFuture

val f2: Future[Long] = someOtherCalcReturningFuture

val result = for(v1 <- f1; v2 <- f2) yield v1 + v2

Cheers,

√

--
Viktor Klang

Akka Tech Lead

Typesafe - The software stack for applications that scale

Twitter: @viktorklang