To reply about:

> I think the two methods Source.lazily and Flow.lazyInit should be
alligned (in their name and in their materialized values)

No, those are different things and should not be name-aligned. The lazyInit
wording is used to talk about “on first element”,
while we use the lazily to mean like Scala’s lazy “on first touching it”.
Hope this clarifies that difference.

-- 
Cheers,
Konrad 'ktoso <http://kto.so>' Malawski
Akka <http://akka.io/> @ Lightbend <http://lightbend.com/>

On March 5, 2018 at 21:31:59, Stefan Wachter (stefan.wach...@gmx.de) wrote:

I just saw that Source.lazily implements a similar concept:

def lazily[T, M](create: () ⇒ Source[T , M]): Source[T, Future[M]]

Here a the materialized value is a Future that is failed if there was no
demand before the source gets never created.

I think the two methods Source.lazily and Flow.lazyInit should be alligned
(in their name and in their materialized values)

*Gesendet:* Montag, 05. März 2018 um 13:13 Uhr
*Von:* "Stefan Wachter" <stefan.wach...@gmx.de>
*An:* akka-user@googlegroups.com
*Betreff:* [akka-user] Akka 2.5.11 - materialization of Flow.lazyInit

Hi,

studying the newly Flow constructor Flow.lazyInit



def lazyInit[I, O, M](flowFactory: I ⇒ Future[Flow[I, O, M]],
fallback: () ⇒ M): Flow[I, O, M]



(cf. https://doc.akka.io/api/akka/2.5.11/akka/stream/scaladsl/Flow$.html) I
wondered how (citation from ScalaDoc)



The materialized value of the `Flow` will be the materializedvalue of
the created internal flow.



could be? Materialization happens before the flow is run. Therefore the
materialized value cannot depend on whether their will be some input or not.

To fix the issue, the materialzed value of Flow.lazyInit should be a
Future[M] or even better a Future[Option[M]]. In case that no internal flow
is materialized it would be a Future[None].

--Stefan


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