Does anyone know of some good articles where a suspending fu kotlinlang #coroutines

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

03/11/2019, 4:48 PM

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

TLDR; wrap your blocking code within

withContext(<http://Dispatchers.IO|Dispatchers.IO>)

if the blocking API call deals with IO.

Example:

Copy code

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

kevin.cianfarini

03/12/2019, 12:09 AM

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

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?

Or reading data from a socket

Marcelo Hernandez

03/12/2019, 12:12 AM

If you have access to a callback, then you can use the

suspendCoroutine

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

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

03/12/2019, 12:18 AM

suspendCoroutine

is what I'm looking for :) thanks

👍 1

Marcelo Hernandez

03/12/2019, 12:19 AM

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

suspendCancellableCoroutine

kevin.cianfarini

03/12/2019, 12:19 AM

Yup sounds like a plan

Thanks

Marcelo Hernandez

03/12/2019, 12:20 AM

You're welcome!

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