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#coroutines
Title
# coroutines
w

withoutclass

12/05/2018, 6:56 PM
So, here is a contrived example of my problem. I am testing suspending function that returns a channel. This function sends some number of items to the channel. If I launch the coroutine for sending items on the channel using the
coroutineScope{}
style of
method2
, sending is always suspended waiting on a receiver, but
method1
does not get suspended(blocked). As far as I can tell, both method 1 and method2 would launch using the same dispatcher (Dispatchers.IO), and that I'm not doing anything "wrong" per se, but clearly I am given I would expect
method1
to not get stuck.
Note that if I make a new
CoroutineScope(coroutineContext)
in
method2
, the code does not block execution. If I use
GlobalScope.launch(coroutineContext)
, the code does not block execution.
I think for now I'm going to stick with
CoroutineScope(coroutineContext).launch
, given it uses parent context and dispatcher without actually blocking the execution of the function launching it
u

uli

12/06/2018, 11:08 AM
`coroutineScope`will wait for all child coroutines to finish, i.e. for
send
to complete. Only then will method2 return the
channel
. Now
send
will not complete until there is a recever...
w

withoutclass

12/06/2018, 3:08 PM
so coroutineScope will effectively block a parent coroutine from executing if a child coroutine suspends?
I guess I just need to alter how I consider scoping things. I can't utilize parent scope of a top level job to create child coroutines in a lower level service. I'll need to have separate scopes, even though I care about stopping the lower level service if my top level job get's cancels/stopped
So this particular example needs to be solved by either: 1. Not having
method
calls launch child coroutines using
coroutineScope
or 2. Providing the channel to the
method
call instead of having the
method
return a new channel
And even then I don't think option 2 would solve the issue, given the parent coroutine would be blocked unable to read from the channel due to
method2
suspending
Anyways this is probably my own fault for not quite being used to the new style, thanks for the help @uli
Is it a good assumption that really,
method1
and
method2
should just be producers from a design perspective?
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