How do you guys handle errors in KMM? For example, I have this use case

interface SignInUseCase {
    @Throws(Exception::class)
    suspend fun execute(email: String, password: String): Whatever
}

When I call this from iOS, I get

signInUseCase.execute(email: email, password: password) { whatever, error in
    // Handle completion
}

Is there a way to have a custom error here, instead of NSError? Ideally, I'd like to have maybe a class or data class

data class Error(
    val title: String
    val detail: String
}

ooh good question

Yeah, I was thinking about that too. So I just have to live with potentially handling two errors? 🙂

So I’m assuming you are dealing with some high level business logic here due to the “Use Case” naming convention

Correct, but I'm just trying out the interface being used from iOS and Android native apps, to see how I can provide only what I needed

Right! and then from your testing you identify that case and catch it somewhere closer to where it’s thrown

Gotcha, so I should parse it as soon as it exits the HttpClient domain and then pass the Result all the way down

Yes, I would do that in this case.

Thank you very much Tim, this was super helpful!

Some cases I would not trickle from HTTP into the business layer though, for example if there was a socket disconnect error.

Just one bonus question - does it make sense to try and use Kotlin's result or I'm better off with just having a custom sealed class?

I would suggest another sealed class, because Kotlin’s is semi-reserved

Yeah, I had some weird issues on iOS side, when using the Kotlin Result

Socket disconnect I might handle and trickle through as a cancel of the coroutine. That one does not go into the result, but it comes through as an exception. I like this, because I don’t want my high level business logic to worry about low-level network issues. Just auth errors.

Hi Guilherme! Thanks for the link, I actually ran into that one, but I can't use Future, as I'm still supporting iOS 12 😞 However, I'll read it again and see if I can parse the sealed class regardless. It's driving me nuts at the moment 🤯