At the moment I get an error that `send` can only be called kotlinlang #coroutines

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Title

aaverin

08/27/2018, 3:48 PM

At the moment I get an error that

send

can only be called in coroutine context, that is hidden by the callback function

Vsevolod Tolstopyatov [JB]

08/27/2018, 4:11 PM

We have

SendChannel<E>.sendBlocking

for this purpose

bj0

08/27/2018, 4:15 PM

or you can use

.offer

if you don't mind dropped events, or are using a conflated channel

aaverin

08/28/2018, 7:07 PM

@Vsevolod Tolstopyatov [JB] I tried using

sendBlocking

but get ClosedSendChannelException code is

produce {
   addSnapshotListener { snapshot ->
     val list = parseSnapshot(snapshot)
     sendBlocking(list)
   }
}

Any ideas why is SendChannel already closed?

What I need is a channel wrapping callback that is executed on every dataset change

Just to clarify I have an active socket connection to a database and every change is delivered in a snapshot callback I need to wrap this callback with coroutine so I could actively subscribe from my client implementation

Vsevolod Tolstopyatov [JB]

08/28/2018, 8:01 PM

SendChannel is closed because you either have closed it or

produce

block ended (e.g. if

addSnapshotListener

is asynchronous)

aaverin

08/28/2018, 8:02 PM

addSnapshotListener

is asynchronous, that’s kind of the point of the code I am trying to write Once in a while I will be getting updates from server socket, and I need to expose them as a channel consumers could subscribe to

To get a single value from socket I am using

suspendCancelableCoroutine

I am trying to find an equivalent in Channels world so I could keep listening the socket and get all updates

bj0

08/28/2018, 8:47 PM

you need something to prevent the

produce

block from suspending, or just use a normal channel

aaverin

08/29/2018, 5:29 AM

I don’t mind

produce

suspending, after all it’s an async operation I am wrapping. Problem is that

send(data)

can only be executed within coroutine body

Still digging through docs and articles trying to figure out what I missed

bj0

08/29/2018, 5:59 AM

ah what i meant to say was "prevent the

produce

block from *ending*", in other words, you need to suspend it somehow

produce

ends -> channel closes

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