Archived project
This is a port of Hamsters FutureOps to Scala 2.13. .
Update June 2026: Hamsters full lib is now compatible with Scala 3 and 2.13
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.
import io.github.hamsters.FutureOps
FutureOps.fromEither(Right("a")) //Future("a")
FutureOps.fromEither(Left(BoomError)) //Future(BoomError)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")Same operations can be used with options : FutureOps.fromOption and squash on Future[Option[A]].
For empty options, an EmptyValueError will be raised.
Add this to you build.sbt :
resolvers += Resolver.bintrayRepo("loicdescotte", "Hamsters")
libraryDependencies += "io.github.scala-hamsters" %% "future-ops" % "1.0.0"