Source.zipWithN

Combine the elements of multiple streams into a stream of sequences using a combiner function.

Source operators

Signature

Source.zipWithNSource.zipWithN

Description

Combine the elements of multiple streams into a stream of sequences using a combiner function.

This operator is essentially the same as using zipN followed by map to turn the zipped sequence into an arbitrary object to emit downstream.

See also:

• zipN
• zip
• zipAll
• zipWith
• zipWithIndex

Example

In this sample we zip three streams of integers and for each zipped sequence of numbers we calculate the max value and send downstream:

Scala

copysourceval numbers = Source(1 :: 2 :: 3 :: 4 :: 5 :: 6 :: Nil)
val otherNumbers = Source(5 :: 2 :: 1 :: 4 :: 10 :: 4 :: Nil)
val andSomeOtherNumbers = Source(3 :: 7 :: 2 :: 1 :: 1 :: Nil)

Source
  .zipWithN((seq: Seq[Int]) => seq.max)(numbers :: otherNumbers :: andSomeOtherNumbers :: Nil)
  .runForeach(println)
// prints:
// 5
// 7
// 3
// 4
// 10

Java

copysourceSource<Integer, NotUsed> numbers = Source.from(Arrays.asList(1, 2, 3, 4, 5, 6));
Source<Integer, NotUsed> otherNumbers = Source.from(Arrays.asList(5, 2, 1, 4, 10, 4));
Source<Integer, NotUsed> andSomeOtherNumbers = Source.from(Arrays.asList(3, 7, 2, 1, 1));

Source.zipWithN(
        (List<Integer> seq) -> seq.stream().mapToInt(i -> i).max().getAsInt(),
        Arrays.asList(numbers, otherNumbers, andSomeOtherNumbers))
    .runForeach(System.out::println, system);
// prints:
// 5
// 7
// 3
// 4
// 10

Note how it stops as soon as any of the original sources reaches its end.

Reactive Streams semantics