Akka Streams - Source.map vs Source.via(flow)

[Ori Popowski]

Hi,

It may seem like a trivial question, but I'm a bit confused about use cases of Source.map vs. Source.via(flow).

For example, these two flows produce the exact same output:

    val flow1 = Source(1 to 10).map(_ * 2).to(Sink.foreach(println))
    val flow2 = Source(1 to 10).via(Flow[Int].map(_ * 2)).to(Sink.foreach(println))

so why would anyone express this functionality with flow2?

Also, in the example given in this blog post, the first way (not using Flows) is used exclusively.

Thanks.

[Endre Varga]

Hi Ori,

The reason is if you have longer, reusable chains of computations then you can factor them out into a Flow. For example if you have a more complex chain handling some deserialization and domain object mapping then you can express it once and then just include it multiple times into other streams. For a simple map this is an overkill of course (btw .map() is converted to a .via() without you seeing it ;) )

-Endre

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[Ori Popowski]

Hi,

I didn't realize that maps underlying implementation is using via. Should have definitely dug into the code more :)

Thanks, it cleared that issue for me.

On Monday, September 5, 2016 at 10:35:10 AM UTC+3, drewhk wrote:

Hi Ori,

The reason is if you have longer, reusable chains of computations then you can factor them out into a Flow. For example if you have a more complex chain handling some deserialization and domain object mapping then you can express it once and then just include it multiple times into other streams. For a simple map this is an overkill of course (btw .map() is converted to a .via() without you seeing it ;) )

-Endre

On Mon, Sep 5, 2016 at 9:30 AM, Ori Popowski <ori...@gmail.com> wrote:

Hi,

It may seem like a trivial question, but I'm a bit confused about use cases of Source.map vs. Source.via(flow).

For example, these two flows produce the exact same output:

    val flow1 = Source(1 to 10).map(_ * 2).to(Sink.foreach(println))
    val flow2 = Source(1 to 10).via(Flow[Int].map(_ * 2)).to(Sink.foreach(println))

so why would anyone express this functionality with flow2?

Also, in the example given in this blog post, the first way (not using Flows) is used exclusively.

Thanks.

--
>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>> Check the FAQ: http://doc.akka.io/docs/akka/current/additional/faq.html
>>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user
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