I created a new video about "Best Practices for using Kotlin Coroutines in Android Development". May...

# coroutines

[Lukas Lechner]

I created a new video about "Best Practices for using Kotlin Coroutines in Android Development". Maybe its helpful for someone!

https://youtu.be/tVDCpjqQ1Ro▾

[Joost Klitsie]

cool video! Luckily I am not surprised by most of it 😄 One question: In the best practice 4, you mention that you can run work in the applicationScope as to make it finish, even if the original calling scope is cancelled. is the `async`/`await` the only way to do this? Or are there also other ways?

[Joost Klitsie]

I ask because Android studio really wants me to turn the `async`/`await` into a withContext(applicationScope.coroutineContext) {..} which doesn't really do the same, as if you do `withContext`and you cancel during it, then the code afterwards will still run and you'd have to do an isActive check:

suspend fun CoroutineScope.test() {
    val result = withContext(applicationScope.coroutineContext) {
        delay(200)
        println("producing 5")
        5
    }
    if (!isActive) { return }
    println(result)
}

[Stylianos Gakis]

Having a function which is both suspending and an extension on CoroutineScope does look a bit suspicious does it not?
In general if a function is an extension on CoroutineScope I expect it to be a fire and continue, just like launch does. Like mentioned here.
And this important quote from the Explicit Concurrency post from Elizarov:
“It leads to the following useful convention: every function that is declared as extension on CoroutineScope returns immediately, but performs its actions concurrently with the rest of the program.”
What are you trying to achieve there Joost, I am a bit confused.

[Joost Klitsie]

@Stylianos Gakis I tried to do a thing that was mentioned in the video, specifically best practice number 4 (using async/await with a differen scope to make work finish even if the original scope gets cancelled). But android studio is giving me a suggestion when I do that to change it to a withContext instead. So my question would be: is this the best way to achieve this behaviour or is there a better way?

[Stylianos Gakis]

And why do you need it to be an extension on CoroutineScope to do that? In the video I see that a CoroutineScope context is introduced by using the coroutineScope {} function, maybe this is what you wanted to use instead?
I may be misunderstanding something, if yes you could show what you would want your code to look like which doesn’t compile and we can take it from there.

[Joost Klitsie]

It is a test sample

[Joost Klitsie]

So it compiles and runs

[Joost Klitsie]

I don't have it as actual code :) but the general idea would be: what is the best way to finish work started from a coroutine when the original scope gets cancelled?

[Joost Klitsie]

Like I load something from the UI, I start a network call, during this my ui moves away and kills its scope, but I still want to finish this backend call.

[Stylianos Gakis]

If you care for the response, I guess you need to do the async approach as shown in the video. If you do not you can simply do val job = appliacationScope.launch{stuff here}; job.join() or not even do the join part if you don’t care for waiting for it to finish.
I don’t know if you can do this without async if you want the response. If someone knows I’d love to see it.

[Joost Klitsie]

cool 🙂 thanks btw for the info and the links you shared!