(I did a quick mock Transaction type, your Monoid should work fine there
ofc).
-- Konrad
On Sunday, 24 April 2016 21:42:43 UTC+2, debasish wrote:
>
> Hi -
>
> I am trying to migrate some akka-streams code from an earlier version
> (akka-stream-experimental 1.0.RC4) .. please have a look at the following ..
>
> /**
> * Create multiple streams out of a single stream. The stream
> "transactions" is being
> * demultiplexed into many streams split by account number. Each of the
> sub-streams are
> * then materialized to the fold sink "txnSink", which folds each of the
> transaction
> * substreams to compute the net value of the transaction for that account
> */
> val netTxn: Source[RunnableGraph[Future[Transaction]], Unit] =
> transactions.map(validate).groupBy(_.accountNo).map { case (a, s) =>
> s.toMat(txnSink)(Keep.right) }
>
> I am trying to create substreams based on a field accountNo within a
> Transaction. Then I pass each substream to toMat with a Sink which is a
> fold Sink defined as below ..
>
> /**
> * Would like to fold transactions through monoid append
> */
> val txnSink: Sink[Transaction, Future[Transaction]] =
> Sink.fold[Transaction, Transaction](TransactionMonoid.zero)(_ |+| _)
>
> The idea is to apply a monoid over each substream and do some netting on
> transactions belonging to the same accountNo.
>
> How can I migrate this to 2.4.4 ? Now groupBy returns a Subflow and I am
> not sure how to apply each of the substreams to the materializer. One
> option that works will be to create a Map[String, Transaction] upfront
> and then directly apply the monoid to the Map in the main stream and not
> create any substream. But I would like to have the substreams fro some
> other purpose as well.
>
> Any help will be appreciated ..
>
> Regards.
> - Debasish
>
>
>
>
>
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