libraryDependencies += "dev.zio" %% "zio-interop-cats" % "<latest-version>"ZIO integrates with Typelevel libraries by providing an instance of Concurrent, Temporal and Async for Task
as required, for instance, by fs2, doobie and http4s.
For convenience, the ZIO library defines an alias as follows:
type Task[A] = ZIO[Any, Throwable, A]Therefore, we provide Cats Effect instances based on this specific datatype.
In order to get a Concurrent[Task] or Concurrent[RIO[R, *]] (note * is kind-projector notation) we need to import zio.interop.catz._:
import cats.effect._
import zio._
import zio.interop.catz._
def ceConcurrentForTaskExample = {
val F: cats.effect.Concurrent[Task] = implicitly
F.racePair(F.unit, F.unit)
}import cats.effect._
import zio._
import zio.interop.catz._
def ceTemporal = {
val F: cats.effect.Temporal[Task] = implicitly
F.sleep(1.second) *> F.unit
}import cats.effect._
import zio._
import zio.interop.catz._
def ceAsync = {
val F: cats.effect.Async[Task] = implicitly
F.racePair(F.unit, F.sleep(1.second) *> F.unit)
}There are many other typeclasses and useful conversions that this library provides implementations for:
- See
zio/interop/cats.scalafile to see all available typeclass implementations for the Cats Effect 3 typeclasses - See
zio/stream/interop/cats.scalafor ZStream typeclass implementations - See
zio/stream/interop/FS2StreamSyntax.scalafor FS2 <-> ZStream conversions
If you only need instances for cats-core typeclasses, not cats-effect import zio.interop.catz.core._:
import zio.interop.catz.core._Note that this library only has an Optional dependency on cats-effect – if you or your libraries don't depend on it, this library will not add it to the classpath.
The following example shows how to use ZIO with Doobie (a library for JDBC access) and FS2 (a streaming library), which both rely on Cats Effect instances (cats.effect.Async and cats.effect.Temporal):
import zio.{durationInt as _, *}
import zio.interop.catz.*
import doobie.*
import doobie.implicits.*
import scala.concurrent.duration.*
object Example extends ZIOAppDefault:
val run = {
val xa: Transactor[Task] =
Transactor.fromDriverManager[Task]("org.h2.Driver", "jdbc:h2:mem:test;DB_CLOSE_DELAY=-1", "user", "", None)
sql"SELECT 42"
.query[Int]
.stream
.transact(xa)
.delayBy(1.second)
.evalTap(i => Console.printLine(i))
.compile
.drain
.exitCode
}Learn more on the ZIO Interop Cats homepage!
For the general guidelines, see ZIO contributor's guide.
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