ZIO is a zero-dependency Scala library for asynchronous and concurrent programming with similar features as Cats IO or Monix.
ZIO — A type-safe, zero-dependency library for asynchronous and concurrent programming in Scala.
Homepage: https://zio.dev/
Questions tagged [zio]
241 questions
27
votes
1 answer
Making sense of Scala FP Libraries
Just for the sake of quick clarity for someone who wants to start working with Scala FP library, on a journey to become better at pure FP.
Would someone clarify the difference/relation between Cats and Cats-Effect, Cats-Effects IO? On top of that,…
MaatDeamon
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11
votes
7 answers
How to test an exception case with zio-test
I have the following function, that I want to test:
def people(id: Int): RIO[R, People]
This function returns People if there is one for that id, resp. fails if not, like:
IO.fail(ServiceException(s"No People with id $id"))
The happy case works,…
pme
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9
votes
1 answer
Experiencing deadlocks when using the Hikari transactor for Doobie with ZIO
I'm using Doobie in a ZIO application, and sometimes I get deadlocks (total freeze of the application). That can happen if I run my app on only one core, or if I reach the number of maximum parallel connections to the database.
My code looks…
fanf42
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8
votes
1 answer
Validation and capturing errors using an algebra
I came across this article on medium: https://medium.com/@odomontois/tagless-unions-in-scala-2-12-55ab0100c2ff. There is a piece of code that I have a hard time understanding. The full source code for the article can be found here:…
boggy
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7
votes
1 answer
How to enforce to run ZIO Tests sequentially
I want to run two integration tests sequentially. How can this be achieved in ZIO Test?
Here is the Suite:
suite("Undeploy a Package")(
testM("There is a Package") {
PackageDeployer.deploy(pckg) *> // first deploy
…
pme
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6
votes
1 answer
Difference in deflate function between Java and C#
I have 2 deflate functions written in C# and Scala, when running with the same input, the returned byte array has a difference in leading bytes and trailing bytes (the difference between the bytes in the middle is expected by the unsigned/signed…
Cypherius
- 521
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6
votes
1 answer
Is there a way to add a descriptive Assert message in a Boolean ZIO Test
I have a couple of Booleans I want to test, like
assert(g8Exists, equalTo(true)) &&
assert(projectExists, equalTo(true)) &&
assert(testenvExists, equalTo(true)) ...
If one fails, all I get is:
false did not satisfy equalTo(true)
No clue which line…
pme
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6
votes
2 answers
ZIO: How to join Fibers for Processes that run forever
I have the following ZIO program with two processes that both run forever:
for {
..
numberProvider <- numberProvider(queue).fork // runs forever
numberService <- numberService(queue) // runs forever
..
}…
pme
- 14,156
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6
votes
4 answers
How to elegantly perform multiple effects in parallel with ZIO
I know that I can use
import zio.Task
def zip3Par[A, B, C](a: Task[A], b: Task[B], c: Task[C]): Task[(A, B, C)] =
a.zipPar(b).zipWithPar(c) { case ((a, b), c) => (a, b, c) }
def zip4Par[A, B, C, D](a: Task[A], b: Task[B], c: Task[C], d:…
Matthias Langer
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5
votes
2 answers
Delegate to a more specific Context Bound (additional implicit parameter)
I am trying to create an example of a ZIO Module, that has two implementations:
Using YAML with circe-yaml
Using HOCON with pureConfig
My general Interface looks like this:
trait Service[R] {
def load[T <: Component](ref: CompRef): RIO[R,…
pme
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- 3
- 52
- 95
5
votes
2 answers
ZIO Fiber orElse generate exception messages
I want to use the combinator orElse on ZIO Fibers.
From docs:
If the first fiber succeeds, the composed fiber will succeed with its result; otherwise, the composed fiber will complete with the exit value of the second fiber (whether success or…
Aleksey N Yakushev
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5
votes
3 answers
ZIO Environment construction
I started experimenting with ZIO, and was trying to run the following highly sophisticated program:
import logger.{Logger, _}
import zio.console._
import zio.{system, _}
object MyApp extends App {
override def run(args: List[String]): ZIO[ZEnv,…
haspok_adv
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5
votes
1 answer
How to share a ZIO Queue between ZIO Tasks via the ZIO Environment
I'm somewhat new to Scala and ZIO and have run into something of an odd puzzle.
I would like to setup a ZIO Environment containing a ZIO Queue and later
have different ZIO Tasks offer and take from this shared Queue.
I tried defining my…
jq170727
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5
votes
0 answers
ZIO interop with Cats on parallel operations
ZIO is not dependent on Cats, so it has its own methods to perform sequence operations: ZIO.sequencePar and ZIO.sequence.
I tried to use sequence provided by interop with Cats and it works the same way as ZIO.sequence:
import zio._
import…
Bogdan Vakulenko
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5
votes
2 answers
What is the right way to send JSON response in http4s?
Not so long time ago I switched from akka-http to http4s. One of the basic things which I wanted to do correctly — JSON handling, in particular sending a JSON response.
I decided to use http4s with ZIO instead of cats, so here is how an http route…
Alex Fruzenshtein
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