They don’t work for me when I’m reading in batches

# coroutines

[withoutclass]

They don’t work for me when I’m reading in batches

[louiscad]

Why so? I'm not sure I understand what you do exactly

[withoutclass]

Making a quick example

[louiscad]

Explaining what you want to do is also useful information

[withoutclass]

So I have an Activity that alters it’s state/responds to information received from incoming bluetooth packets. I do not want to thrash the UI, so I want to read in all the packets, then delay some time before checking to see if there are more packets.

[withoutclass]

internal suspend fun listenForPackets(packetBroadcastChannel: BroadcastChannel<Packet>, 
    activityActionChannel: SendChannel<Action>) {
    val packetReceiveChannel = packetBroadcastChannel.openSubscription()
    try {
        while (isActive) {
            delay(4000)
            var count = 0
            while (!packetReceiveChannel.isEmpty) {
                packetReceiveChannel.receive()
                count++
            }

            when (count) {
                0 -> activityActionChannel.send(Action.DoThing)
            }

        }
    } finally {
        withContext(NonCancellable) {
            packetReceiveChannel.cancel()
        }
    }
}

[withoutclass]

this is where I landed after discovering the requirement to call cancel in a finally block.

[withoutclass]

In essence, I want to “batch” read all packets from the channel till it’s empty, then delay for some time before doing so again

[louiscad]

Is the packetBroadcastChannel parameter Activity bound or application bound in regards to its lifecycle?

[withoutclass]

application bound, it’s attached to a long running service

[withoutclass]

It also could be that I don’t quite understand consume

[withoutclass]

I’m thinking another solution could be to use a pipeline, where a producer takes in a BroadcastChannel, consuming each element, and caches them for some delay before producing them.

[withoutclass]

apparently use() will also work which I did not know

[withoutclass]

openSubscription().use {}

[louiscad]

@withoutclass openSubscription() returns a new ReceiveChannel which you can consume without closing the source BroadcastChannel, so it should work for you in place of use (and is more explicit regarding the consumption of a channel). What you are looking for though is probably some "debounce". See this gist by @kevinherron (and mind my comment on it to be sure you consume the channel properly 😉 ) https://gist.github.com/kevinherron/5a895911a45eb5752ff247a205d618b7

[kevinherron]

@louiscad thanks for the comment. funny, I actually had it in a consumeEach originally, but changed it while debugging and never switched back