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ZIO Cheat Sheet

  • This is based on ZIO 2.0.X (in particular 2.0.10).
  • For simplicity, ZIO environment has been omitted but all the functions also work with the form ZIO[R, E, A].
  • Function arguments are usually by name, but that has (mostly) been ignored for simplicity. Also, functions are often "more generic" in their parameter types than shown below.
  • For many functions there are several (unmentioned) related functions that are conceptually similar but differ in some detail. They are usually easy to learn due to consistent naming.
  • Important ZIO types other than the functional effect type ZIO[R, E, A] have been left out. For example: ZStream[R, E, A], ZLayer[RIn, E, ROut], Fiber[E, A] and Ref[A].
  • In the remainder of this cheat sheet, E1 >: E, but E2 can be any error type. Also A1 >: A.

Aliases

Alias Full Form
UIO[A] ZIO[Any, Nothing, A]
IO[E, A] ZIO[Any, E, A]
Task[A] ZIO[Any, Throwable, A]
RIO[R, A] ZIO[R, Throwable, A]
URIO[R, A] ZIO[R, Nothing, A]

Creating effects

Name Given To
ZIO.succeed => A IO[Nothing, A]
ZIO.fail => E IO[E, Nothing]
ZIO.interrupt IO[Nothing, Nothing]
ZIO.die Throwable IO[Nothing, Nothing]
ZIO.attempt => A IO[Throwable, A]
ZIO.async ((IO[E, A] => Unit) => Unit)
FiberId		 IO[E, A]
ZIO.fromEither Either[E, A] IO[E, A]
ZIO.left A IO[Nothing, Either[A, Nothing]]
ZIO.right B IO[Nothing, Either[Nothing, B]]
ZIO.fromFiber Fiber[E, A] IO[E, A]
ZIO.fromFuture ExecutionContext => Future[A] IO[Throwable, A]
ZIO.fromOption Option[A] IO[Option[Nothing], A]
ZIO.none IO[Nothing, Option[Nothing]]
ZIO.some A IO[Nothing, Option[A]]
ZIO.fromTry Try[A] IO[Throwable, A]
ZIO.acquireReleaseWith IO[E, A] (acquire)
A => IO[Nothing, Any] (release)
A => IO[E, B] (use)		 IO[E, B]
ZIO.when Boolean
IO[E, A]		 IO[E, Option[A]]
ZIO.whenZIO IO[E, Boolean]
IO[E, A]		 IO[E, Option[A]]
ZIO.whenCase A
PartialFunction[A, IO[E, B]]		 IO[E, Option[B]]
ZIO.whenCaseZIO IO[E, A]
PartialFunction[A, IO[E, B]]		 IO[E, Option[B]]
ZIO.filter Iterable[A]
A => IO[E, Boolean]		 IO[E, List[A]]
ZIO.cond Boolean
A
E		 IO[E, A]

Transforming effects

Name From Given To
map IO[E, A] A => B IO[E, B]
mapAttempt IO[Throwable, A] A => B IO[Throwable, B]
as IO[E, A] B IO[E, B]
asSome IO[E, A] IO[E, Option[A]]
asSomeError IO[E, A] IO[Option[E], A]
orElseFail IO[E, A] E2 IO[E2, A]
unit IO[E, A] IO[E, Unit]
flatMap IO[E, A] A => IO[E1, B] IO[E1, B]
flatten IO[E, IO[E1, A]] IO[E1, A]
mapBoth IO[E, A] E => E2
A => B		 IO[E2, B]
mapError IO[E, A] E => E2 IO[E2, A]
mapErrorCause IO[E, A] Cause[E] => Cause[E2] IO[E2, A]
flatMapError IO[E, A] E => IO[Nothing, E2] IO[E2, A]
collect IO[E, A] E1
PartialFunction[A, B]		 IO[E1, B]
sandbox IO[E, A] IO[Cause[E], A]
flip IO[E, A] IO[A, E]
tap IO[E, A] A => IO[E1, _] IO[E1, A]
tapBoth IO[E, A] E => IO[E1, _]
A => IO[E1, _]		 IO[E1, A]
tapError IO[E, A] E => IO[E1, _] IO[E1, A]
absolve IO[E, Either[E, A]] IO[E, A]
some IO[E, Option[A]] IO[Option[E], A]
head IO[E, List[A]] IO[Option[E], A]
toFuture IO[Throwable, A] IO[Nothing, Future[A]]
filterOrDie IO[E, A] A => Boolean
Throwable		 IO[E, A]
filterOrDieMessage IO[E, A] A => Boolean
String		 IO[E, A]
filterOrElse IO[E, A] A => Boolean
A => IO[E, A]		 IO[E, A]
filterOrFail IO[E, A] A => Boolean
E		 IO[E, A]
when IO[E, A] Boolean IO[E, Option[A]]
unless IO[E, A] Boolean IO[E, Option[A]]

Declaring and providing the environment

Name From Given To
ZIO.service given Tag[A] ZIO[A, Nothing, A]
provideEnvironment ZIO[R, E, A] ZEnvironment[R] IO[E, A]
provideLayer ZIO[R, E, A] ZLayer[R0, E, R] ZIO[R0, E, A]

Configuration

Name From Given To
ZIO.config Config[A] IO[Config.Error, A]

Recover from errors

Name From Given To
either IO[E, A] IO[Nothing, Either[E, A]]
option IO[E, A] IO[Nothing, Option[A]]
ignore IO[E, A] IO[Nothing, Unit]
exit IO[E, A] IO[Nothing, Exit[E, A]]
<> (orElse) IO[E, A] IO[E2, A1] IO[E2, A1]
orElseEither IO[E, A] IO[E2, B] IO[E2, Either[A, B]]
fold IO[E, A] E => B
A => B		 IO[Nothing, B]
foldZIO IO[E, A] E => IO[E2, B]
A => IO[E2, B]		 IO[E2, B]
foldCauseZIO IO[E, A] Cause[E] => IO[E2, B]
A => IO[E2, B]		 IO[E2, B]
catchAll IO[E, A] E => IO[E2, A1] IO[E2, A1]
catchAllCause IO[E, A] Cause[E] => IO[E2, A1] IO[E2, A1]
catchSome IO[E, A] PartialFunction[E, IO[E1, A1]] IO[E1, A1]
retry IO[E, A] Schedule[E, S] IO[E, A]
eventually IO[E, A] IO[Nothing, A]

Terminate fiber with errors

Name From Given To
orDie IO[Throwable, A] IO[Nothing, A]
orDieWith IO[E, A] E => Throwable IO[Nothing, A]
refineOrDie IO[Throwable, A] PartialFunction[Throwable, E2] IO[E2, A]
refineOrDieWith IO[E, A] PartialFunction[E, E2]
E => Throwable		 IO[E2, A]

Combining effects parallelism

Name From Given To
ZIO.foldLeft Iterable[A]
S
(S, A) => IO[E, S]		 IO[E, S]
ZIO.foreach Iterable[A]
A => IO[E, B]		 IO[E, List[B]]
ZIO.foreachPar Iterable[A]
A => IO[E, B]		 IO[E, List[B]]
ZIO.collectAll Iterable[IO[E, A]] IO[E, List[A]]
ZIO.collectAllPar Iterable[IO[E, A]] IO[E, List[A]]
ZIO.forkAll Iterable[IO[E, A]] IO[Nothing, Fiber[E, List[A]]]
fork IO[E, A] IO[Nothing, Runtime[E, A]]
<*> (zip) IO[E, A] IO[E1, B] IO[E1, (A, B)]
*> (zipRight) IO[E, A] IO[E1, B] IO[E1, B]
<* (zipLeft) IO[E, A] IO[E1, B] IO[E1, A]
<&> (zipPar) IO[E, A] IO[E1, B] IO[E1, (A, B)]
&> (zipParRight) IO[E, A] IO[E1, B] IO[E1, B]
<& (zipParLeft) IO[E, A] IO[E1, B] IO[E1, A]
race IO[E, A] IO[E1, A1] IO[E1, A1]
raceAll IO[E, A] Iterable[IO[E1, A1]] IO[E1, A1]
raceEither IO[E, A] IO[E1, B] IO[E1, Either[A, B]]

Finalizers

Name From Given To
ensuring IO[E, A] UIO[_] IO[E, A]
onError IO[E, A] Cause[E] => UIO[_] IO[E, A]
onInterrupt IO[E, A] UIO[_] IO[E, A]
onTermination IO[E, A] Cause[Nothing] => UIO[_] IO[E, A]

Timing and repetition

Name From Given To
ZIO.never IO[Nothing, Nothing]
ZIO.sleep Duration IO[Nothing, Unit]
delay IO[E, A] Duration IO[E, A]
timeout IO[E, A] Duration IO[E, Option[A]]
timed IO[E, A] IO[E, (Duration, A)]
forever IO[E, A] IO[E, Nothing]
repeat IO[E, A] Schedule[A, B] IO[E, B]
repeatUntil IO[E, A] A => Boolean IO[E, A]
repeatWhile IO[E, A] A => Boolean IO[E, A]

Logging

Name From Given To
ZIO.log String IO[Nothing, Unit]
ZIO.logFatal String IO[Nothing, Unit]
ZIO.logError String IO[Nothing, Unit]
ZIO.logWarning String IO[Nothing, Unit]
ZIO.logInfo String IO[Nothing, Unit]
ZIO.logDebug String IO[Nothing, Unit]
ZIO.logTrace String IO[Nothing, Unit]

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ZIO Cheat Sheet

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