Fix an explanation of flowOn Operator

[seyoungcho2]

In this part, it says :

Otherwise, if changing dispatcher is required, it collects flow emissions in one coroutine that is run using a specified [context] and emits them from another coroutines with the original collector's context

and this explanation is reversed.

If flowOn passes CoroutineDispatcher, then the flow's emissions are performed in a coroutine running with the specified CoroutineContext not collector's context. The collector's original context is used to collect values emitted from the flow.

You can easily configure this by running below code.

val numberFlow: Flow<Int> = flow {
    for (number in 1..3) {
        println("[${Thread.currentThread().name}] Emitting: $number")
        emit(number)
        delay(1000)
    }
}

fun main() = runBlocking<Unit> {
    numberFlow
        .flowOn(Dispatchers.IO) 
        .collect { value ->
            println("[${Thread.currentThread().name}] Collected: $value")
        }
}

The result of code is:

[DefaultDispatcher-worker-1 @coroutine#2] Emitting: 1
[main @coroutine#1] Collected: 1
[DefaultDispatcher-worker-1 @coroutine#2] Emitting: 2
[main @coroutine#1] Collected: 2
[DefaultDispatcher-worker-1 @coroutine#2] Emitting: 3
[main @coroutine#1] Collected: 3

Process finished with exit code 0

The new coroutine(coroutine#2) is using DefaultDispatcher-worker-1 of Dispatchers.IO. And runBlocking Coroutine(coroutine#1) is collecting the value.

[dkhalanskyjb]

Thanks!