I've got a `Flow` which I'm running `collectLatest()` on, but it's only firing the first time I send...

# coroutines

[reactormonk]

I've got a Flow which I'm running collectLatest() on, but it's only firing the first time I send something into it, not the second time... what can be the reasons here?

[Trevor Stone]

Do you have a code example you can provide

[reactormonk]

Trying to get some logs, but adb keeps SIGABRTing on me

[Trevor Stone]

A low tech way to debug is to just place .onEach{println()} at different places in the flow

[reactormonk]

My favourite way. println debugging. Wait, gotta refactor some code.

[reactormonk]

This is the consuming part:

val scope = CoroutineScope(Job() + <http://Dispatchers.IO|Dispatchers.IO>)

        val readerFlow = merge(disconnectedFlow, acsBluetoothReaderManager.onReaderDetection())

        scope.launch {
            readerFlow.onEach {
                Log.d("BTM", "Got a new reader to collect: $it")
            }
                .collectLatest { reader ->

The producing part:

private val disconnectedFlow: MutableStateFlow<BluetoothReaderSupport?> = MutableStateFlow(null)
    private fun disconnectedCallback() {
        Log.d("BTM", "Disconnected Callback")
        val scope = CoroutineScope(Job())
        scope.launch {
            disconnectedFlow.emit(null)
        }
    }

The other producing part:

fun BluetoothReaderManager.onReaderDetection(): Flow<BluetoothReaderSupport?> {
    val brm = this
    return callbackFlow<BluetoothReaderSupport?> {
        brm.setOnReaderDetectionListener { reader ->
            trySendBlocking(BluetoothReaderSupport(reader))
                .onSuccess { Log.d("BluetoothSupport", "Forwarded new reader: $reader") }
                .onFailure { exception -> throw exception!! }
        }
        awaitClose { brm.setOnReaderDetectionListener(null) }
    }
}

```

[reactormonk]

I've got a D/BTM: Disconnected Callback log line, but nothing afterwards.

[reactormonk]

Oh duh, StateFlow vs. SharedFlow.
Changed it to:

private val disconnectedFlow = MutableSharedFlow<BluetoothReaderSupport?>()
    private fun disconnectedCallback() {
        Log.d("BTM", "Disconnected Callback")
        if (disconnectedFlow.tryEmit(null)) {
            Log.d("BTM", "Emitted empty reader")
        } else {
            Log.w("BTM", "couldn't emit empty reader")
        }
    }

But the tryEmit gives me a false 🤔

[louiscad]

@reactormonk set the extraBufferCapacity to 1 in the MutableSharedFlow