Thanks.
I tried to put example using same:
val source = Source (1 to 5).filter(x=> x%2==0)
val sink:Sink[Int, Future[Int]]=Sink.fold[Int,Int](0)(_ + _)
val runnableGraph = source.via(counter[Int]).toMat(sink)(Keep.left)
val result=runnableGraph.run()
def counter[T]: Flow[T, T, Counter] = {
val internalCounter = new AtomicLong(0)
Flow[T].map{ elem ⇒
internalCounter.incrementAndGet()
elem
}.mapMaterializedValue(_ ⇒ new Counter{
override def get = internalCounter.get
})
}
The result should give me a tuple having count (flow) and sum (Sink) value,
since I am using Keep.both,* but it is giving only Future[Int].*
what is difference between materialize value and out?
Thanks
Arun
On Saturday, March 5, 2016 at 6:46:12 PM UTC-6, Rafał Krzewski wrote:
>
> Hi,
> there are a few ways of doing that. Probably the simplest one is using
> Flow.mapMaterializedValue. Suppose you'd like to create a Flow that counts
> the elements that pass through it and makes the current count available
> through a "side channel":
>
> trait Counter {
> def get: Long
> }
>
> def counter[T]: Flow[T, T, Counter] = {
> val internalCounter = new AtomicLong(0)
> Flow[T].map{ elem ⇒
> internalCounter.incrementAndGet()
> elem
> }.mapMaterializedValue(_ ⇒ new Counter{
> override def get = internalCounter.get
> })
> }
>
> Another way is using a GraphStageWithMaterializedValue while building a
> custom Flow / Sink / Source. Instead of returning a GraphStageLogic, like
> an ordinary GraphStage, you return a pair of GraphStageLogic and the
> materialized value.
>
> Cheers,
> Rafał
>
> W dniu niedziela, 6 marca 2016 01:02:56 UTC+1 użytkownik Arun Sethia
> napisał:
>>
>> Hi,
>>
>> can some explain what does it mean of materialized value ? I have see
>> documentation at
>> http://doc.akka.io/docs/akka-stream-and-http-experimental/2.0.3/scala/stream-quickstart.html#transforming-and-consuming-simple-streams
>>
>>
>> I am not sure how Flow can define materialize type, for example the
>> following code has Input - Tweet, output - Int but Mat is Unit. I would
>> like to see how someone can define Mat as Int or any example where Flow or
>> source is defining Mat other than Unit.
>>
>> - val count: Flow[Tweet, Int, Unit] = Flow[Tweet].map(_ => 1)
>>
>>
>>
>> It is quite confusing for me to understand difference between "out" and
>> "Mat".
>>
>>
>> Thanks
>>
>> As
>>
>>
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