Suspend a call until a value is set - kotlin

Question

I want class UploadWorker to retrieve a value from class Manager, but that value may not yet be ready in Manager. So I want class UploadWorker to wait until that value is set.
class UploadWorker(appContext: Context, workerParams: WorkerParameters):
Worker(appContext, workerParams) {
override fun doWork(): Result {
Manager.isReady()
return Result.success()
}
}
object Manager {
private lateinit var isReady
fun initialize(context: Context, myData: MyData) {
...
isReady = true
}
suspend fun isReady() {
if(::isReady.isInitialized()
return isReady
else // wait here until initialized
}
}
In the else if I could somehow suspend or wait until my MyApplication class calls initialize(). Any ideas?

Answer 1

CompletableDeferred is quite handy for situations like this.
Your code would probably look something like this:
object Manager {
private val initialized = CompletableDeferred<Unit>()
fun initialize(context: Context, myData: MyData) {
...
initialized.complete(Unit)
}
suspend fun awaitInitialized() {
initialized.await()
// initialization is done at this point
}
}

Answer 2

You can use StateFlow to deliver status of initialization:
val isReady = MutableStateFlow(false)
// to wait:
if (isReady.value) return true
else isReady.first { it } // it == true
// to notify:
isReady.value = true
Although StateFlows are quite lightweight, but if you want to do it more lighter but in a ugly way (using coroutine internals directly):
val conts = mutableListOf<Continuation<Boolean>>()
private lateinit var isReady = false
set(value) {
if (value) conts.forEach { it.resume(true) }.also { conts.clear() }
field = value
}
// to wait:
if (isReady) return true
else suspendCancellableCoroutine { cont ->
conts.add(cont)
invokeOnCancellation { conts.remove(cont) }
}
// to notify:
isReady = true