Does anyone know of some good articles where a sus...

# coroutines

[kevin.cianfarini]

Does anyone know of some good articles where a suspending function is written that deals with something like IO? I want to learn about composing a suspending function from resources which aren't suspending

[Marcelo Hernandez]

Perhaps this might help https://medium.com/@elizarov/blocking-threads-suspending-coroutines-d33e11bf4761

[Marcelo Hernandez]

TLDR; wrap your blocking code within withContext(<http://Dispatchers.IO|Dispatchers.IO>) if the blocking API call deals with IO.

[Marcelo Hernandez]

Example:

suspend fun getUser(userId: String) = withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
    dataStore.getUser(userId) // Blocking database query
}

[kevin.cianfarini]

@Marcelo Hernandez I just used IO as an example. I'm trying to get to the low level nitty gritty of coroutine's.

[kevin.cianfarini]

For example, if I wanted to call an external process and wait for that process to finish and join, how would I wrap that call and make it a suspending function?

[kevin.cianfarini]

Or reading data from a socket

[Marcelo Hernandez]

If you have access to a callback, then you can use the suspendCoroutine or suspendCancellableCoroutine builders.
https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.coroutines/suspend-coroutine.html
https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/suspend-cancellable-coroutine.html

[Marcelo Hernandez]

Otherwise, if it truly is blocking, then withContext is what you'll have to wrap the blocking call with in order to run it within a suspend function.

[kevin.cianfarini]

suspendCoroutine is what I'm looking for :) thanks

[Marcelo Hernandez]

If the blocking call is cancellable in any way, then it is recommended to use suspendCancellableCoroutine.

[kevin.cianfarini]

Yup sounds like a plan

[kevin.cianfarini]

Thanks

[Marcelo Hernandez]

You're welcome!