Hello, I'm looking for a structure that act as Semaphore , Defered and MVar but which is a state machine. Aka blocking while the state is not in the expected state.
I think I could do something like that with
I think I could do something like that with
Ref but I'm not sure how I could make the wait part. Is there is that look like that which exists or is there good exemple that can help me to make this?
oh modify is enought in fact to know what happen inside the update !
So if there were a variant that took a function to
F[A] that would be potentially problematic
@SystemFw I made that with your exemple https://gist.github.com/crakjie/7398a57124690f09a7e2037fc3112457 I still have to try it next week but I'm quite happy.
I was lucky that when looking for a state machine with
I was lucky that when looking for a state machine with
Ref+ Deferred you actually already made one !
(and if they don't too bad for them, I did appreciate it, so I'm gonna share it no matter if the do or don't xD )
I don't have a talk specifically on that, but I do cover it in a few talks (shared state in pure FP, my fs2 talk at klarna), I do have a long reddit post on it though. If you browse through https://systemfw.org/talks and https://systemfw.org/writings you should find all the links you need
the reddit posts are called "the benefits of IO"
I think it's the one from Italy, so Shared State in Pure FP :) thanks, mate
@LukaJCB I do, but in more up-to-date ones :)
you’re best of just writing your own
Bracket instance
Anyways thank you.
in fact there could be a
Bracket for any MonadError
getting the prioritization right would be tricky though
(ResourceProxy stuff we’ve discussed a few times)
I would like to seek help refactoring this code. I don't know if should wrap the ValidatedNec to IO or what... I also wanted to have a logger on every validation.
type ValidationResult[A] = ValidatedNec[JobPostError, A]
override def createJobPost(
newJobPost: JobPost
): IO[ValidatedNec[String, JobPost]] = {
// TODO: Add logger here on every field validation
val localValidation: ValidationResult[JobPost] = (
validateNoop(newJobPost.id),
validateEmptiness("Job post title".some, newJobPost.title),
validateEmptiness("Job post description".some,
newJobPost.description),
validateNoop(newJobPost.createdAt),
validateNoop(newJobPost.modifiedAt)
).mapN(JobPost)
val databaseValidations: IO[ValidationResult[JobPost]] = (for {
_ <- Logger[ConnectionIO].info("Validating job title")
title <- validateTitleExistence(newJobPost)
_ <- Logger[ConnectionIO].info("Validating job description")
description <- validateNoop(newJobPost.description).pure[ConnectionIO]
createdAt <- validateNoop(newJobPost.createdAt).pure[ConnectionIO]
modifiedAt <- validateNoop(newJobPost.modifiedAt).pure[ConnectionIO]
id <- validateNoop(newJobPost.id).pure[ConnectionIO]
} yield {
(id, title, description, createdAt, modifiedAt).mapN(JobPost)
}).transact(xa)
val response: IO[ValidatedNec[String, JobPost]] =
localValidation match {
case Valid(_) => databaseValidations.map(_.leftMap(_.map(_.errorMessage)))
case Invalid(e) => e.map(_.errorMessage).invalid[JobPost].pure[IO]
}
response
}
Or is there much better way to do this in case that I just want to validate some of the case class fields?
actually you never use the
Valid case in your result, so you don't even need the last clause