Is there something similar to `IO.handleError { }`...

# arrow

[Ryan Benasutti]

Is there something similar to IO.handleError { } that doesn't require I provide an IO<A> (perhaps one which requires an IO<Unit>)? I have a method which returns an IO<A>, but I need to guarantee certain additional IO operations happen if the former IO fails (and in this case, I can't return an IO<A> because that part failed).

[raulraja]

if this is related to ensuring resource safety and properly closing things you can use bracketCase

[raulraja]

bracketing guarantees finalisers are invoked no matter what even in the presence of external cancelation

[simon.vergauwen]

If you provide a snippet I'd happily help you write it with bracketCase or similar operators to satisfy your use case :)

[Ryan Benasutti]

Untitled.kt

[Ryan Benasutti]

Hopefully this makes sense. inputFile doesn't get deleted if the command fails (because it fails with an exception).

[simon.vergauwen]

Untitled.kt

[simon.vergauwen]

It first creates the file, and when the command in use fails it is guaranteed to go through release.

It’s similar to try-with-resources except that it works within IO so it supports concurrency, parallelism, cancellation etc while guaranteeing resource safety 🙂

[Ryan Benasutti]

Maybe I am missing a dependency, but bracketCase is showing as an unresolved reference

[simon.vergauwen]

If you have IO on the classpath than you should also have bracketCase IIRC.

[Ryan Benasutti]

IO has bracketCase, yes, but IOEffect does not

[simon.vergauwen]

Why are you using IOEffect? And IOEffect should extend from Async and thus also Bracket.

[Ryan Benasutti]

You are using IOEffect. Your code uses IO.effect which resolves as fun Companion.effect(): IOEffect = object : arrow.effects.extensions.IOEffect { }

[Ryan Benasutti]

Oh, the problem is there is a compiler error earlier on

[Ryan Benasutti]

effect is a zero argument method, but you pass it a lambda

[simon.vergauwen]

What version on Arrow are you on? I have master in my head 😅

[Ryan Benasutti]

0.9.0

[simon.vergauwen]

I'm on my phone. Oh yeah I'm talking about snapshot

[simon.vergauwen]

I can help rewrite to 0.9 when I'm home

[Ryan Benasutti]

If I just omit effect and make a normal IO then it works

[simon.vergauwen]

That works fine 2