Hi all :android-wave: , A couple of questions rega...

# coroutines

[Abhimanyu]

Hi all 👋 ,
A couple of questions regarding this code.
1. Is this correct?
2. Any way to improvise this code?

private suspend fun getData(): MyData {
        return coroutineScope {
            val data1 = async(
                context = dispatcherProvider.io,
            ) {
                getData1UseCase()
            }
            val data2 = async(
                context = dispatcherProvider.io,
            ) {
                getData2UseCase()
            }
            val data3 = async(
                context = dispatcherProvider.io,
            ) {
                getData3UseCase()
            }

            MyData(
                data1 = data1.await(),
                data2 = data2.await(),
                data3 = data3.await(),
            )
        }
    }

[Abhimanyu]

getData1UseCase() -> Returns a list of Data1 type.
getData2UseCase() -> Returns a list of Data2 type.
getData3UseCase() -> Returns a list of Data3 type.

I want to fetch all the data in parallel.
So, using async for each use case call.

[kevin.cianfarini]

Looks okay to me

[kevin.cianfarini]

If you really wanted to, you could:

suspend fun foo() {
  return withContext(<http://dispatcherProvider.io|dispatcherProvider.io>) {
    val first = async { ... }
    val second = async { ... }
    return MyData(first.await(), second.await())
  }
}

[Geert]

If you already have a dependency on Arrow, you could also use its parZip function:

suspend fun getUser(id: UserId): User =
parZip(
{ getUserName(id) },
{ getAvatar(id) }
) { name, avatar -> User(name, avatar) }

[uli]

Bit late, but I have a small improvement for you. You can use awaitAll to fail faster, when one of the tasks fail. awaitAll will cancel the first tasks (and all others) as soon as one of the later fail. Otherwise it’s the same:

val (data1, data2, data3) = awaitAll(
                async(
                    context = dispatcherProvider.io,
                ) {
                    getData2UseCase()
                }, 
                async(
                    context = dispatcherProvider.io,
                ) {
                    getData2UseCase()
                },
                async(
                    context = dispatcherProvider.io,
                ) {
                    getData2UseCase()
                }
            )
    MyData(data1, data2, data3)

[Abhimanyu]

Oh nice, I was actually using await all, but I changed from that as it was returning a list and I had to type cast the result.

I didn't think about destructuring.

Thanks for sharing this. @uli .