How can I await (or run infinitely a function in o...

# coroutines

[polendina]

How can I await (or run infinitely a function in order to listen to keep listening to events). I know this might sound a bit odd, but I'm not really doing actual tests for my codebase, but rather trying to learn more about Firebase's SDK (which is apparently only accessible through Android), and hence I found that running Unit tests on the JVM is the best way to deal to go about this (without having to deal with an emulator/physical device overhead)

@Test
fun retrieveData() = runTest(timeout = Duration.INFINITE) {
    Firebase.firestore
        .collection("gaming").document("gaming")
        .get()
        .addOnFailureListener {
            println("Failure")
        }
        .addOnSuccessListener {
            println(it.data)
        }
        .addOnCompleteListener {
            println("Done")
        }
        .await()
        .let {
            println(it.data) // Only this line prints
        }
}

[Leon Kiefer]

You can wrap subscriptions using Flow, have a look at the callbackFlow builder

[polendina]

@Leon Kiefer
I've tried to convert the callback to a suspend function

suspend fun getDocument() = suspendCoroutine { continuation ->
    Firebase.firestore
        .collection("gaming")
        .document("gaming")
        .get()
        .addOnCompleteListener {
            continuation.resume(true)
        }
        .addOnFailureListener { exception ->
            continuation.resume(null)
        }
        .addOnSuccessListener { result ->
            continuation.resume(result)
        }
     }

but it never returns

[Leon Kiefer]

You can call getDocument with a timeout using withTimeout, also you should pass the exception of the callback to the continuation

[Leon Kiefer]

For the Firebase SDK there are also kotlin extensions for coroutines already I think, so you don't need write them yourself

[polendina]

> call getDocument with a timeout
I was just curious why it doesn't invoke any of the callbacks in any of those cases
> kotlin extensions for coroutines
Ya. I was just reading about it in terms how things evolved from java callbacks, and that behavior piqued my interest

[louiscad]

Firebase already has Flow extensions with the KTX artifact. Those have been reviewed by the community to be correct. BTW, never use suspendCoroutine, it can lead to memory leaks because it can prevent cancellation from happening. Use suspendCancellabeCoroutine instead.