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scalaakkaakka-stream

Akka-stream, trigger action once I received a number of items?

I am looking for an "aggregator" block in akka-streams. For instance a block that waits until it has received 3 strings and then triggers an action - like evaluating the average length - and propagate downstream the result of the action.

The flow would wait to receive three strings, say

"hallo"
"boat"
"cat"

then evaluate the average length

4

and send it downstream. What's the easiest way to achieve this?

Solution

  • It depends on requirement but in your particular case you can do

    Source(List(1, 2, 3, 4, 5, 6, 7))
  .grouped(3)
  .map { chunk =>
    chunk.sum / 3.0
  }

    You can do variation of this using .scan as well.