I'm not sure if I'm doing something wrong or there...

# arrow-contributors

[aballano]

I'm not sure if I'm doing something wrong or there's something fishy when trying to run code on Android's main thread:

// Android's fragment code
override fun onResume() {
    super.onResume()
    unsafe {
        runBlocking {
            fx {
                println("DEBUG onResume 0 $threadName")
                continueOn(NonBlocking)
                println("DEBUG onResume 1 $threadName")
                continueOn(Dispatchers.Default)
                println("DEBUG onResume 2 $threadName")
                continueOn(Dispatchers.Main)
                println("DEBUG onResume main $threadName")
            }
        }
    }
}

output is:

DEBUG onResume 0 main
DEBUG onResume 1 ForkJoinPool-1-worker-2
DEBUG onResume 2 DefaultDispatcher-worker-2

[gildor]

Correct, because you use runBlocking

[gildor]

code inside of coroutine is dispatched on threads which you requested, but runBlockling blocks thread and wait child coroutine and suspend function

[aballano]

how would be the appropriate way to run this on Android then?

[gildor]

just use launch instead

[aballano]

but would that work on top of Arrow?

[gildor]

I don’t know

[gildor]

In general you should start some background coroutine on background thread

[aballano]

the thing is that switching to other threads works as seen in the output, the problem is when trying to go back to the main thread

[aballano]

and the idea is to do it on top of arrow (reason why I ask here 🙂)

[gildor]

your problem is runBlocking

[gildor]

not thread switching

[gildor]

runBlocking blocks thread exactly what you shouldn’t do on main thread

[gildor]

but if you use runBlocking, it means that you already have dependency on kotlinx.coroutines, isn’t it?

[pakoito]

No launch here @gildor, we’re doing our own coroutines runtime 😉

[gildor]

I see

[gildor]

how you may launch async background task in Arrow?

[pakoito]

runNonBlocking

[gildor]

😀

[gildor]

pretty stright-forward name 👍

[pakoito]

same file, same interface. next function 😛

[pakoito]

https://github.com/arrow-kt/arrow/blob/master/modules/effects/arrow-effects-data/src/main/kotlin/arrow/effects/typeclasses/UnsafeRun.kt#L9

[gildor]

I see, yeah, make sense

[simon.vergauwen]

Soon we'll add interop with kotlinx again. So you'll be able to run fx code with launch/async.

[simon.vergauwen]

But you might lose the optimisation we have in our runners. Hard to 100% confirm that already.