zipLatest

Combines elements from each of multiple sources into tuples Pair and passes the tuples pairs downstream, picking always the latest element of each.

Fan-in operators

Signature

Source.zipLatestSource.zipLatest Flow.zipLatestFlow.zipLatest

Description

Combines elements from each of multiple sources into tuples Pair and passes the tuples pairs downstream, picking always the latest element of each.

No element is emitted until at least one element from each Source becomes available.

Example

Scala

copysourceval numbers = Source(1 :: 2 :: Nil)
val letters = Source("a" :: "b" :: Nil)

numbers.zipLatest(letters).runForeach(println)
// this will print
// (1,a)
// (2,a)
// (2,b)
// NOTE : The output is not always deterministic and also depends on order of elements flowing from the streams.
// Sometimes the output could also be :
// (1, a)
// (1, b)
// (2, b)

Java

copysource
Source<Integer, NotUsed> numbers = Source.from(Arrays.asList(1, 2));
Source<String, NotUsed> letters = Source.from(Arrays.asList("a", "b"));

numbers.zipLatest(letters).runForeach(System.out::println, system);
// this will print
// Pair(1,a)
// Pair(2,a)
// Pair(2,b)

//
// NOTE : The output is not always deterministic and also depends on order of elements flowing
// from the streams.
// Sometimes the output could also be :
// Pair(1, a)
// Pair(1, b)
// Pair(2, b)

Reactive Streams semantics