I don t understand why `currentScope` is deprecated For exam kotlinlang #coroutines

suspend fun httpGetAsync(): Deferred<String> = currentScope {
    async {
        // ... Do HTTP GET
    }
}

suspend fun main() {
  coroutineScope {
    val request1 = httpGetAsync()
    val request2 = httpGetAsync()
    
    println("${request1.await()} - ${request2.await()")
  }
}

httpGetAsync

was using

coroutineScope

, it means that

request2

will be filled when

request1

is completely done.

Jonathan

10/05/2018, 12:13 PM

You should avoid returning

Job

Deferred

and make funciton suspend or extension of

CoroutineScope

suspend fun httpGet(): String = withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
  // ... Do HTTP GET
  "result"
}

suspend fun main() {
  coroutineScope {
    val request1 = async { httpGet() }
    val request2 = async { httpGet() }

    println("${request1.await()} - ${request2.await()}")
  }
}

A suspending function which returns a deferred is actually very strange. It basically means promising the future of a value... Always remember that a suspending function is the exact equivalent of a function returning a promise 😉

Albert

10/05/2018, 12:20 PM

thanks@Jonathan. that makes sense. I tend to compare it with C# time to time, which I shouldn't do

streetsofboston

10/05/2018, 2:14 PM

@Albert Yes, try to avoid using `Deferred`s and use “plain”

suspend

function instead. If you really need to handle some special coordination and cancellation between calling and getting the results of `suspend`ed functions, wrap them in an

async

block, which will return a

Deffered

, which you then can use to get results or cancel.

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