Cats Helper
ClockHelper
import com.evolutiongaming.catshelper.ClockHelper._
val clock = Clock.const[Id](nanos = 1000, millis = 2)
clock.millis // 2
clock.nanos // 1000
clock.micros // 1
clock.instant // Instant.ofEpochMilli(2)SerialRef
Like Ref but allows A => F[A] rather than A => A
Ensures that updates are run serially
import com.evolutiongaming.catshelper.SerialRef
for {
ref <- SerialRef.of[IO, Int](0)
_ <- ref.update(a => (a + 1).pure[IO])
} yield {}LazyVal
Functional alternative to lazy keyword in Scala
trait LazyVal[F[_], A] {
def get: F[A]
def getLoaded: F[Option[A]]
}ToFuture & FromFuture
trait ToFuture[F[_]] {
def apply[A](fa: F[A]): Future[A]
}
trait FromFuture[F[_]] {
def apply[A](future: => Future[A]): F[A]
}ToTry & FromTry
trait ToTry[F[_]] {
def apply[A](fa: F[A]): Try[A]
}
trait FromTry[F[_]] {
def apply[A](fa: Try[A]): F[A]
}Log
trait Log[F[_]] {
def debug(msg: => String): F[Unit]
def info(msg: => String): F[Unit]
def warn(msg: => String): F[Unit]
def warn(msg: => String, cause: Throwable): F[Unit]
def error(msg: => String): F[Unit]
def error(msg: => String, cause: Throwable): F[Unit]
}Runtime
trait Runtime[F[_]] {
def availableCores: F[Int]
def freeMemory: F[Long]
def totalMemory: F[Long]
def maxMemory: F[Long]
def gc: F[Unit]
}ThreadLocalRef
trait ThreadLocalRef[F[_], A] {
def get: F[A]
def set(a: A): F[Unit]
def update(f: A => A): F[Unit]
def modify[B](f: A => (A, B)): F[B]
}ResourceFenced
This is useful to ensure release called at most once, in cases when "unsafe" api like Resource.allocated being used
val resource: Resource[F, A] = ???
resource.fencedReadWriteRef
A mutable reference to A value with read-write lock semantics.
FeatureToggled
Manages a given Resource[F, A] providing access to it only when a feature-toggle is on.
val serviceResource: Resource[F, AService] = ???
val flag: F[Boolean] = ???
val ftService: Resource[F, Resource[F, Option[AService]]] = FeatureToggled
.polling(
serviceResource,
flag,
pollInterval = 10.seconds,
gracePeriod = 30.seconds,
)
ftService.use { access =>
access.use {
case Some(service) => service.doStuff(…)
case None => F.unit
}
}PureTest
This helper lives in a separate cats-helper-testkit module. It is makes testing F[_]-based code easier.
NOTE: cats-helper-testkit is an experimental module and may break SemVer guarantees from time to time.
However we will do our best to avoid unnecessary breakages.
"what time is it now?" in PureTest[IO].of { env =>
import env._
for {
_ <- IO.sleep(1.hour)
_ <- testRuntime.getTimeSinceStart.map(_ shouldBe 1.hour)
} yield ()
}Setup
addSbtPlugin("com.evolution" % "sbt-artifactory-plugin" % "0.0.2")
libraryDependencies += "com.evolutiongaming" %% "cats-helper" % "2.2.3"