Hello. I have a question about combining coroutines and `Result<T>`. I have the code like fol...

# coroutines

[kawmra]

Hello. I have a question about combining coroutines and Result<T>.

I have the code like following:

launch {
    runCatching { doSomething() }
        .onSuccess {
            doSuccessProcess(it)
        }
        .onFailure {
            doFailureProcess()
        }
}

I wanna handle errors if doSomething() fails.
But this code catches CancellationException as well when launch was canceled.
Are there any problems? Can I just ignore the CancellationException?

[gildor]

But what should happen in case of cancellation?

[gildor]

it looks for me as valid behavior

[gildor]

you requested for some result, cancellation means that result is not ready

[kawmra]

oh, I see. you’re right.
I want to just ignore the result if it canceled.

[kawmra]

btw, does it not impede the propagation of cancellations?

[gildor]

how you can do that in theory?

[gildor]

You can do something like this of course to ignore:

runCatching { 
try { doSomething() } catch (e: CancellationException) { someDefault() }
}

[gildor]

also, I don’t see reason in general for this usage of runBlocking with launch, you do not return any result, why not just use try/catch, so you can check exception type

[kawmra]

doSomething() returns value and it may throw exceptions too.
And I can’t list up those exceptions in advance.

[gildor]

Not sure what you mean, I meant this:

try {
  doSomething()
} catch(e: CancellationException) {
   //Do nothning
} catch(e: Exception) {
  doFailureProcess()
}

[kawmra]

doSomething returns value, so I meant:

val value = try {
  doSomething()
} catch (e: CancellationException) {
  return
} catch (e: Exception) {
  doFailureProcess()
  return
}
doSuccessProcess(value)

Yes, try/catch style is possible, but I prefer Result<T> style because it is more readable than try/catch one.

My question was "CancellationException will be caught by runCatching", and you did let me notice that it is a surely exception because it was cancelled so I need handle the exception.
So the question was already solved.
I am always grateful for your help!

[gildor]

👍