Table of contents
My app on the Google play store
Resources
Programming Android with Kotlin: Achieving Structured Concurrency with Coroutines. Chapter 10
Short code example
- Here is the code that will allow you to make automatic retries on a flow:
fun <T, R : Any> Flow<T>.mapWithRetry(
action: suspend (T) -> R,
predicate: suspend (R, attempt: Int) -> Boolean
) = map { data ->
var attempt = 0L
var shallRetry: Boolean
var lastValue: R? = null
do {
val tr = action(data)
shallRetry = predicate(tr, (++attempt).toInt())
if (!shallRetry) lastValue = tr
} while (shallRetry)
return@map lastValue
}
twitchEmoteImpl.getChannelEmotes(
oAuthToken,clientId,broadcasterId
).mapWithRetry(
action={
// result is the result from getChannelEmotes()
// if you wanted to do any manipulation to the
// request you would do it here
result -> result
},
predicate = { result, attempt ->
val repeatResult = result is Response.Failure && attempt < 3
repeatResult
}
).collect{
// do what you would normally do once a flow is emitted
}
-
result -> resultrepresents the code not doing any sort of manipulation of the result emitted from the flow
Why use this?
- There are times when the request fails and the best solution is to simply make another request. Instead of forcing your user to manually make another request. We can implement this function that will automatically make 3 requests if it fails. We will not inform the users of the extra requests. Instead they should only be informed after the 3 failed attempts
- However, be aware that we should not do this on every failed request. On requests that fail due to authentication or no available network errors, we should avoid making multiple requests and simply inform the user of the failed request.
Conclusion
- Thank you for taking the time out of your day to read this blog post of mine. If you have any questions or concerns please comment below or reach out to me on Twitter.
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