[2.0 - Scala] Multiple async calls

[Meeraj Kunnumpurath]

Hi,

What is the best way to use async HTTP in a controller that makes multiple outbound WS calls such that the response is returned after all the calls complete?

Kind regards

Meeraj

[Pascal Voitot Dev]

You can use a wonderful feature from Promise:
Promise.sequence(List[Promise[A]]): Promise[List[A]]

You can provide it with a List (or any sequence) of promises and it returns a Promise of List meaning it redeems all Promises before redeemining the Promise[List].
So you can launch several WS calls in parallel and it will await for responses in an asynchronous and non-blocking way...

A Promise can embed other promises etc... So you can build a tree of promises etc...

interesting isn't it?

br
Pascal

Meeraj

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[Nourhan El Malahy]

Guys, please how can I pop-up a message when the user clicks on a certain button?? 

[Pascal Voitot Dev]

please don't pollute another thread...
open a new thread if you have a specific question

thanks
Pascal

[Nourhan El Malahy]

I'm Sorry, I didn't notice! I wrote it here by mistake!

[Meeraj Kunnumpurath]

Thanks Pascal, I will have a look at that. Yes, I did see a passing reference to this in the Play docco.

Regards
Meeraj

[Meeraj Kunnumpurath]

Hi Pascal,

Thanks for your suggestion, it works like a dream. I have the code below, if it is of any help to anyone else.

def makeCall() = Action { implicit request =>

    def scheduleCalls(callIds : Seq[String], request : Request[AnyRef]) : List[Promise[Response]] = {
        if (callIds.isEmpty) {
            return List()
        } else {
            val promise = WS.url("https://callUrl" + callIds.head).post("")
            promise :: scheduleCalls(callIds.tail, request)
        }
    }

    Async {
        val callIds = request.body.asFormUrlEncoded.get("callId")
        val promises = Promise.sequence(scheduleCalls(callIds, request))
        promises.map { response =>
            Ok("Ok")
        }
    }

}

Regards
Meeraj

On Wed, Apr 25, 2012 at 9:06 PM, Pascal Voitot Dev <pascal.v...@gmail.com> wrote:

[Pascal Voitot Dev]

One of the great features of Play2 ;)

You're welcome ;)