Is there any difference in : ```suspend fun getFlow() = withContext(<http://Dispachers.IO|Dispachers...

# coroutines

[Juan Rada]

Is there any difference in :

suspend fun getFlow() = withContext(<http://Dispachers.IO|Dispachers.IO>) {
     flow { ... }
}

and

fun getFlow() = flow { ... }.flowOn(<http://Dispachers.IO|Dispachers.IO>)

[Joffrey]

Yes, the first one doesn't make sense, and doesn't do what you think it does

[Joffrey]

In the first example, withContext will only affect the creation of the flow (which is very quick because it doesn't execute the body of the flow builder). It will suspend the caller and potentially do a context switch just for an instant, just the time it takes to instantiate a flow and return it. Only the flow instantiation and the return will be executed in the IO dispatcher.

[Joffrey]

In the second example, the caller is not suspended at all, a flow is constructed immediately, and the body of the flow itself will be executed on the IO dispatcher when the flow is collected. The creation of the flow and the return are executed in the caller's thread

[Juan Rada]

ohh got it so I guess the equivalent function of flowOn will be

suspend fun getFlow() =  flow {
    withContext(Dispatchers.IO) {  }
}

[Mikhail]

flowOn affects not only flow {} block but also any map, transform and similar functions in chain before flowOn call. In your example behavior will be the same, but if you add map between flow {} and flowOn behavior will become different

[Peter Farlow]

Generally, do not use withContext inside the flow { } flow builder. If you try to call emit inside the withContext block, it will throw an exception. You should use flowOn if you want to change the dispatcher on which the flow executes the code

[myanmarking]

i don’t think withContext will do anything really, i might be wrong. There is no suspension point in the function

[Peter Farlow]

I had assumed that code was omitted for brevity