fs2.interop.flow

Implementation of the reactive-streams protocol for fs2; based on Java Flow.

Attributes

See also

java.util.concurrent.Flow

Example

scala> import cats.effect.IO
scala> import fs2.Stream
scala> import java.util.concurrent.Flow.Publisher
scala>
scala> val upstream: Stream[IO, Int] = Stream(1, 2, 3).covary[IO]
scala> val publisher: Stream[IO, Publisher[Int]] = upstream.toPublisher
scala> val downstream: Stream[IO, Int] = publisher.flatMap { publisher =>
    |   Stream.fromPublisher[IO](publisher, chunkSize = 16)
    | }
scala>
scala> import cats.effect.unsafe.implicits.global
scala> downstream.compile.toVector.unsafeRunSync()
res0: Vector[Int] = Vector(1, 2, 3)

Members list

Type members

Classlikes

Attributes

Source: syntax.scala
Supertypes: class Object

trait Matchable

class Any
Self type: syntax.type

Value members

Concrete methods

Creates a Stream from a subscribe function; analogous to a Publisher, but effectual.

This function is useful when you actually need to provide a subscriber to a third-party.

Value parameters

chunkSize: setup the number of elements asked each time from the Publisher. A high number may be useful if the publisher is triggering from IO, like requesting elements from a database. A high number will also lead to more elements in memory. The stream will not emit new element until, either the Chunk is filled or the publisher finishes.
subscribe: The effectual function that will be used to initiate the consumption process, it receives a Subscriber that should be used to subscribe to a Publisher. The subscribe operation must be called exactly once.

Attributes

See also

the overload that only requires a Publisher.

Note

The subscribe function will not be executed until the stream is run.

Example

scala> import cats.effect.IO
scala> import fs2.Stream
scala> import java.util.concurrent.Flow.{Publisher, Subscriber}
scala>
scala> def thirdPartyLibrary(subscriber: Subscriber[Int]): Unit = {
    |  def somePublisher: Publisher[Int] = ???
    |  somePublisher.subscribe(subscriber)
    | }
scala>
scala> // Interop with the third party library.
scala> fs2.interop.flow.fromPublisher[IO, Int](chunkSize = 16) { subscriber =>
    |   IO.println("Subscribing!") >>
    |   IO.delay(thirdPartyLibrary(subscriber)) >>
    |   IO.println("Subscribed!")
    | }
res0: Stream[IO, Int] = Stream(..)

Source

package.scala

Creates a Stream from a Publisher.

Value parameters

chunkSize: setup the number of elements asked each time from the Publisher. A high number may be useful if the publisher is triggering from IO, like requesting elements from a database. A high number will also lead to more elements in memory. The stream will not emit new element until, either the Chunk is filled or the publisher finishes.
publisher: The Publisher to consume.

Attributes

See also

the toStream extension method added to Publisher

Note

The Publisher will not receive a Subscriber until the stream is run.

Example

scala> import cats.effect.IO
scala> import fs2.Stream
scala> import java.util.concurrent.Flow.Publisher
scala>
scala> def getThirdPartyPublisher(): Publisher[Int] = ???
scala>
scala> // Interop with the third party library.
scala> Stream.eval(IO.delay(getThirdPartyPublisher())).flatMap { publisher =>
    |   fs2.interop.flow.fromPublisher[IO](publisher, chunkSize = 16)
    | }
res0: Stream[IO, Int] = Stream(..)

Source

package.scala

Allows subscribing a Subscriber to a Stream.

The returned program will run until all the stream elements were consumed. Cancelling this program will gracefully shutdown the subscription.

Value parameters

stream: the Stream that will be consumed by the subscriber.
subscriber: the Subscriber that will receive the elements of the stream.

Attributes

Source: package.scala

Creates a Publisher from a Stream.

The stream is only ran when elements are requested. Closing the Resource means not accepting new subscriptions, but waiting for all active ones to finish consuming. Canceling the Resource.use means gracefully shutting down all active subscriptions. Thus, no more elements will be published.

Value parameters

stream: The Stream to transform.

Attributes

See also: unsafeToPublisher for an unsafe version that returns a plain Publisher.

subscribeStream for a simpler version that only requires a Subscriber.
Note: This Publisher can be reused for multiple Subscribers, each Subscription will re-run the Stream from the beginning.
Source: package.scala

Creates a Publisher from a Stream.

The stream is only ran when elements are requested.

Value parameters

stream: The Stream to transform.

Attributes

See also: toPublisher for a safe version that returns a Resource.
Note: This Publisher can be reused for multiple Subscribers, each Subscription will re-run the Stream from the beginning.
Source: package.scala

Concrete fields

A default value for the chunkSize argument, that may be used in the absence of other constraints; we encourage choosing an appropriate value consciously.

A default value for the chunkSize argument, that may be used in the absence of other constraints; we encourage choosing an appropriate value consciously. Alias for defaultBufferSize.

Attributes

Note: the current value is 256.
Source: package.scala

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