Does kotlin coroutines have async call with timer?
Does Kotlin has possibility to call function async() in coroutines with some time, witch will return default result after time completion?
I found that it's possible to only call await, and than infinity wait the result.
async {
...
val result = computation.await()
...
}
But real production case than you need to return either default result or exception. What is proper way to do something in Kotlin coroutines? Like something similar to this:
async {
...
val timeout = 100500
val result: SomeDeferredClass = computation.await(timeout)
if (result.isTimeout()) {
// get default value
} else {
// process result
}
...
}
You can use the withTimeout -function. It will throw a CancellationException when it times out. You could catch this exception and return your default value.
Something like this:
async {
...
val timeout = 100500L
try {
withTimeout(timeout) {
computation.await()
}
...
} catch (ex: CancellationException) {
defaultValue
}
}
You could also use the withTimeoutOrNull -function, which returns null on timeout. Like this:
async {
...
val timeout = 100500L
withTimeoutOrNull(timeout) { computation.await() } ?: defaultValue
}
This approach won't let you differentiate between a timeout and a computation that returns null though. The default value would be returned in both cases.
For more info, see here: https://github.com/Kotlin/kotlinx.coroutines/blob/master/coroutines-guide.md#timeout
Combining both Extensions and @marstran solution I came to a solution that may fit better to your requirements of having the await function with timeout and default value. Also I think it's a cleaner solution
Just define the extension function:
suspend fun <T> Deferred<T>.await(timeout : Long, defaultValue : T) =
withTimeoutOrNull(timeout) { await() } ?: defaultValue
And you can use it anywhere. Instead of
async {
...
val timeout = 100500L
withTimeoutOrNull(timeout) { computation.await() } ?: defaultValue
}
You can do simply
async {
val timeout = 100500L
computation.await(timeout, defaultValue)
}
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