FutureOps

This is a port of Hamsters FutureOps to Scala 2.13.

Goal

Monad stacks are not easy to compose (e.g. in a for comprehension), and if you don't want to use Monad transformers you can use this Future additional methods.

FutureOps.fromEither

import io.github.hamsters.FutureOps

FutureOps.fromEither(Right("a")) //Future("a")
FutureOps.fromEither(Left(BoomError)) //Future(BoomError)

squash Future[Either[Throwable, A]] and Future[Try[A]]

You can use squash on a Future[Either[Throwable, A]] to get a Future[A].

import FutureOps._

abstract class Error(message: String) extends Exception(message)
case object BoomError extends Error("Boom")

val fea: Future[Either[Error, String]] = Future(Right("a"))
val feb: Future[Either[Error, String]] = Future(Left(BoomError))

fea.squash //Future("a")
feb.squash //Future(BoomError)

You can also squash on a Future[Try[A]] to get a Future[A] in much the same way:

import FutureOps._

val fta: Future[Try[String]] = Future(Success("a"))
val ftb: Future[Try[String]] = Future(Failure(new Exception("Boom")))

fta.squash //Future("a")
ftb.squash //Future(Exception("Boom"))

It can also be useful to compose several Future[Either[Throwable, _]] without monad transformers :

def fea: Future[Either[Throwable, Int]] = Future(Right(1))
def feb(a: Int): Future[Either[Throwable, Int]] = Future(Right(a + 2))

val composedAB: Future[Int] = for {
  a <- fea.squash
  ab <- feb(a).squash
} yield ab

composedAB // Future("ab")

val error: Either[Throwable, Int] = Left(BoomError)
val composedABWithError: Future[Int] = for {
  a <- Future.successful(error).squash
  ab <- feb(a).squash
} yield ab

composedABWithError //Future(Failure(BoomError))

Composing several Future[Try[_]]s without monad transformers is also possible:

def fta: Future[Try[Int]] = Future(Success(1))
def ftb(a: Int): Future[Try[Int]] = Future(Success(a + 2))

val composedAB: Future[Int] = for {
  a <- fta.squash
  ab <- ftb(a).squash
} yield ab

composedAB // Future("ab")

Options

Same operations can be used with options : FutureOps.fromOption and squash on Future[Option[A]]. For empty options, an EmptyValueError will be raised.

Install

Add this to you build.sbt :

resolvers += Resolver.bintrayRepo("loicdescotte", "Hamsters") 
libraryDependencies += "io.github.scala-hamsters" %% "future-ops" % "1.0.0"