Does nesting `withContext(IO)` inside another `wit...

# coroutines

[Fernando Sanchez (Perraco Labs)]

Does nesting withContext(IO) inside another withContext(IO) produce a thread switch, even if both use the same dispatcher? Or, when exiting the nested withContext(IO), is it guaranteed that execution will continue on the same thread without a switch, since the dispatcher is the same?

[streetsofboston]

The answer above (emoji) says "no".

However, IIRC, when suspend and then resuming within the same dispatcher, there is thread _affinity_: The thread will very likely be the same, no switch is done. However, I'm not sure that this is a 100% guarantee.

[KarolK]

AFAIK there's no guarantee that the thread will stay the same. That's why in Android we have Dispatchers.Main.immediate which is the only one which gives that guarantee.