If i have an either: `val result: Either<VdsErr...

# arrow

[Chris Paul]

If i have an either: val result: Either<VdsError, VdsData>

and these error data types:

sealed class VdsError {
    object NotFound: VdsError()
    object SystemError: VdsError()
}

is there a simple way to map on success, but also on NotFound, but break out of the mapping if SystemError?

eg

result.map { data ->
    doSomething()
    data
}

basically conditionally map some failure circumstances but ignore others?

I thought perhaps a conditional mapLeft would do this, but the problem is that mapLeft then returns a Left rather than a Right and then you immediately exit

hope this makes sense, I'm still quite new to these sort of functional types.

[Chris Paul]

I can side step the problem by changing it Either<VdsError, VdsData?> and then eliminating the NotFound error but I feel like there should be another solution

[aballano]

for Either you have handleErrorWith witch should do what you want if you add a conditional check for the NotFound

[Chris Paul]

hmm

[aballano]

result.handleErrorWith {
  if (it == NotFound) //recover
  else it.left()
}

[Chris Paul]

couldn't find that in the docs

[Chris Paul]

that is very useful thankyou

[Haris Khan]

@Chris Paul If you're looking for docs on it: https://arrow-kt.io/docs/arrow/typeclasses/applicativeerror/

[Chris Paul]

yea i found that after I googled Alberto's answer. It's good to have that documentation, but I only found it once I knew what I was looking for

[Haris Khan]

It's certainly a miss that it's not on the page with Either, I agree.