JarCastingInterop Future
This library provides an interoperability layer with Scala's Future.
From Future
This is the extension method added to IO companion object:
def fromFuture[A](ftr: () => Future[A])(ec: ExecutionContext): Task[A] =
There are a few things to clarify here:
ftr, the expression producing theFuturevalue, is a thunk (orFunction0). The reason for that is,Futureis eager, it means as soon as you callFuture.applythe effect has started performing, that's not a desired behavior in Pure FP (which ZIO encourages). So it's recommended to declare expressions creatingFutures usingdefinstead ofval.- Also you have to be explicit on which EC you want to use, having it implicit, as in the standard library, is a bad practice.
- Finally, as you can see, the
IOreturned fixes the error type toThrowablesince that's the only possible cause for a failedFuture.
Example
// EC is not implicit
val myEC: ExecutionContext = ...
// future defined in thunk using def
def myFuture: Future[ALotOfData] = myLegacyHeavyJobReturningFuture(...)
val myIO: Task[ALotOfData] = IO.fromFuture(myFuture _)(myEC)
To Future
This extension method is added to values of type Task[A]:
def toFuture: UIO[Future[A]]
Notice that we don't actually return a Future but an infallible IO producing the Future when it's performed, that's again because as soon as we have a Future in our hands, whatever it does is already happening.
As an alternative, a more flexible extension method is added to any IO[E, A] to convert to Future as long as you can provide a function to convert from E to Throwable.
def toFutureE(f: E => Throwable): UIO[Future[A]]
Example
val safeFuture: UIO[Future[MoarData]] = myShinyNewApiBasedOnZio(...).toFuture(MyError.toThrowable)
val itsHappening: Future[MoarData] = unsafeRun(safeFuture)
