DOes it make sense to use Arrow FX and Flow from coroutines?

# arrow

[Jimmy Alvarez]

DOes it make sense to use Arrow FX and Flow from coroutines?

[simon.vergauwen]

Absolutely. Arrow Fx is build on top of KotlinX Coroutines, and it relies on Flow as a streaming data type.

We hope to add extend the functionality of Flow further like we did for suspend.
For example, Arrow Fx has support for Schedule and Flow for retrying.

https://arrow-kt.io/docs/apidocs/arrow-fx-coroutines/arrow.fx.coroutines/kotlinx.coroutines.flow.-flow/retry.html

[Jimmy Alvarez]

Given that with flow it is possible to represent errors, what will be the purpose of using either ?

[simon.vergauwen]

It's only possible with Flow to represent errors in the Throwable domain. Just like suspend.
It doesn't offer any utilities to model errors in a typed manner, that is where Either comes in. It works the same whether you use suspend or Flow.

For example:

/** Returns a single [User] for a given [Id] or [UserNotFound] if [User] doesn't exist for [Id] *//
suspend fun fetchUser(id: Id): Either<UserNotFound, User> = TODO()

fun flowUsers(ids: Flow<Int>): Flow<Either<UserNotFound, User>> = ids.map { id -> fetchUser(id) }