Introduction to ZSink

A ZSink[R, E, I, L, Z] is used to consume elements produced by a ZStream. You can think of a sink as a function that will consume a variable amount of I elements (could be 0, 1, or many!), might fail with an error of type E, and will eventually yield a value of type Z together with a remainder of type L as leftover.

To consume a stream using ZSink we can pass ZSink to the ZStream#run function:

import zio._
import zio.stream._

val stream = ZStream.fromIterable(1 to 1000)
val sink   = ZSink.sum[Int]
val sum    = stream.run(sink)

ZSink has one type alias called Sink. Sink[E, A, L, B] is a type alias for ZSink[Any, E, A, L, B]. We can think of a Sink as a function that does not require any services and will consume a variable amount of A elements (could be 0, 1, or many!), might fail with an error of type E, and will eventually yield a value of type B. The L is the type of elements in the leftover.

type Sink[+E, A, +L, +B] = ZSink[Any, E, A, L, B]