👀 Views: 0 💬 Answers: 1 📅 Created: 2025-08-21

scala cats-effect future Scala

I'm testing a new approach and I've been working on this all day and I recently switched to I've been banging my head against this for hours. I'm working with Scala 2.13 and trying to implement a higher-kinded type using Cats Effect's `IO` to wrap a function that returns a `Future`. However, I'm running into type safety issues when trying to combine these types. Here's a simplified version of what I've tried: ```scala import cats.effect.{IO, IOApp} import scala.concurrent.ExecutionContext.Implicits.global import scala.concurrent.Future object MyApp extends IOApp { def fetchData(): Future[String] = Future { Thread.sleep(1000) "Fetched Data" } def run(args: List[String]): IO[ExitCode] = { val io: IO[String] = IO.fromFuture(IO(fetchData())) io.flatMap(data => IO(println(data))).as(ExitCode.Success) } } ``` However, when I try to run this, I get a compilation behavior: `want to prove that Future[String] is a valid IO[String]`. I feel like I'm missing something fundamental about how the `IO.fromFuture` works. I've looked through the Cats Effect documentation and found the method signature: ```scala def fromFuture[A](future: Future[A])(implicit ec: ExecutionContext): IO[A] ``` But I'm unsure why I'm getting that type mismatch behavior. I've also tried wrapping the Future in an IO explicitly first, like this: ```scala val futureIO: IO[Future[String]] = IO(fetchData()) ``` But that didn’t resolve the scenario either. Any insights into how I can properly handle this situation and ensure type safety? Is there a better pattern I should be following? Thanks in advance! For context: I'm using Scala on Linux. Any advice would be much appreciated. I'm working with Scala in a Docker container on Ubuntu 20.04. What are your experiences with this? I'm working in a Debian environment. Has anyone dealt with something similar?