I have 5 api call function in the viewModel that I want to called parallel how can I do this? I put each of the function in the WithContext(Dispachers.IO) but it's not working. I used coroutines flow for calling api.
Note: I used clean architecture pattern and I have single use-case
ViewModel codes:
class MyJobsViewModel constructor(
private val myJobsUseCases: MyJobsUseCases,
private val clientNavigator: ClientNavigator
) : ViewModel(), ClientNavigator by clientNavigator {
private val _state = mutableStateOf(MyJobsState())
val state: State<MyJobsState> get() = _state
private fun getAllJobs(
offset: Int = 0,
limit: Int = 10,
type: JobTypeEnum = JobTypeEnum.ALL
) {
myJobsUseCases.getJobsUseCase.invoke(offset = offset, limit = limit, type = type)
.onEach {
when (it) {
is Resource.Success -> _state.value =
state.value.copy(
isLoading = false,
allJobItems = it.data ?: JobItemsResponse()
)
is Resource.Error -> _state.value =
state.value.copy(
isLoading = false,
error = it.message ?: "An unexpected error occurred"
)
is Resource.Loading -> _state.value = state.value.copy(isLoading = true)
}
}.launchIn(viewModelScope)
}
private fun getActiveJobs(
offset: Int = 0,
limit: Int = 10,
type: JobTypeEnum = JobTypeEnum.ALL
) {
myJobsUseCases.getJobsUseCase.invoke(offset = offset, limit = limit, type = type)
.onEach {
when (it) {
is Resource.Success -> _state.value =
state.value.copy(
isLoading = false,
activeJobItems = it.data ?: JobItemsResponse()
)
is Resource.Error -> _state.value =
state.value.copy(
isLoading = false,
error = it.message ?: "An unexpected error occurred"
)
is Resource.Loading -> _state.value = state.value.copy(isLoading = true)
}
}.launchIn(viewModelScope)
}
}
The best way to parallel multiple calls is to follow structured concurrency principle.
For example, when you need to evaluate the result of 5 independent network requests:
suspend fun fetchA(): Int { /* ... */ }
suspend fun fetchB(): Int { /* ... */ }
suspend fun fetchC(): Int { /* ... */ }
suspend fun fetchD(): Int { /* ... */ }
suspend fun fetchE(): Int { /* ... */ }
suspend fun overallResult(): Int = coroutineScope {
val a = async { fetchA() }
val b = async { fetchB() }
val c = async { fetchC() }
val d = async { fetchD() }
val e = async { fetchE() }
a.await() + b.await() + c.await() + d.await() + e.await()
}
Or when you need to make 5 independent api calls without returning any value:
suspend fun callA() { /* ... */ }
suspend fun callB() { /* ... */ }
suspend fun callC() { /* ... */ }
suspend fun callD() { /* ... */ }
suspend fun callE() { /* ... */ }
suspend fun makeCalls(): Unit = coroutineScope {
launch { callA() }
launch { callB() }
launch { callC() }
launch { callD() }
launch { callE() }
}
Wrapping function in launch or async block produces a new coroutine and executes in parallel.
coroutineScope organizes the area where launch and async can be used. It completes only when every child coroutine is completed.
Related
I'm aware that there are a couple of topics on this but none of them solve my issue.
I'm trying to test an implementation of NetworkBoundResource.
inline fun <ResultType, RequestType, ErrorType> networkBoundResource(
crossinline query: () -> Flow<ResultType>,
crossinline fetch: suspend () -> Response<RequestType>,
crossinline saveFetchResult: suspend (RequestType) -> Unit,
crossinline onFetchFailed: (Response<*>?, Throwable?) -> ErrorType? = { _, _ -> null },
crossinline shouldFetch: (ResultType) -> Boolean = { true },
coroutineDispatcher: CoroutineDispatcher
) = flow<Resource<ResultType, ErrorType>> {
val data = query().first()
emit(Resource.Success(data))
if (shouldFetch(data)) {
val fetchResponse = safeApiCall { fetch() }
val fetchBody = fetchResponse.body()
if (fetchBody != null) {
saveFetchResult(fetchBody)
}
if (!fetchResponse.isSuccessful) {
emit(Resource.Error(onFetchFailed(fetchResponse, null)))
} else {
query().map { emit(Resource.Success(it)) }
}
}
}.catch { throwable ->
emit(Resource.Error(onFetchFailed(null, throwable)))
}.flowOn(coroutineDispatcher)
This works as expected in my use case in production code.
override suspend fun getCategories() = networkBoundResource(
query = {
categoryDao.getAllAsFlow().map { categoryMapper.categoryListFromDataObjectList(it) }
},
fetch = {
categoryServices.getCategories()
},
onFetchFailed = { errorResponse, _ ->
categoryMapper.toError(errorResponse)
},
saveFetchResult = { response ->
// Clear the old items and add the new ones
categoryDao.clearAll()
categoryDao.insertAll(categoryMapper.toDataObjectList(response.data))
},
coroutineDispatcher = dispatchProvider.IO
)
I have my test setup like this (using turbine for flow testing).
#OptIn(ExperimentalCoroutinesApi::class)
class NetworkBoundResourceTests {
data class ResultType(val data: String)
sealed class RequestType {
object Default : RequestType()
}
sealed class ErrorType {
object Default : RequestType()
}
private val dispatchProvider = TestDispatchProviderImpl()
#Test
fun `Test`() = runTest {
val resource = networkBoundResource(
query = { flowOf(ResultType(data = "")) },
fetch = { Response.success(RequestType.Default) },
saveFetchResult = { },
onFetchFailed = { _, _ -> ErrorType.Default },
coroutineDispatcher = dispatchProvider.IO
)
resource.test {
}
}
}
The coroutine dispatcher is set to unconfined through DI/Test dispatcher.
I want to test that;
Emitting first data from query, then query is updated and new data from saveFetchResult then query().map { emit(Resource.Success(it)) } emits the updated data from that save result.
I think I need to do something around a spyk on my flow with MockK but I can't seem to figure it out. query() will always return the same flow of data as it's mocked to do so if I awaitItem() again it returns the same data (as it should) as that's what the mock is setup for.
I've found a way to test this. Not exactly how I imagined it in my head.
#Test
fun `Given should fetch is true and fetch throws exception, When retrieving data, Then cached items emitted and error item after`() =
runTest {
val saveFetchResultAction = mockk<(() -> Unit)>("Save results action")
val fetchErrorAction = mockk<(() -> ErrorType)>("Fetch error action")
every { fetchErrorAction() } answers { ErrorType }
val fetchRequestAction = mockk<(() -> Response<RequestType>)>("Fetch request action")
coEvery { fetchRequestAction() } throws (Exception(""))
networkBoundResource(
query = { flowOf(ResultType) },
fetch = { fetchRequestAction() },
saveFetchResult = { saveFetchResultAction() },
onFetchFailed = { _, _ -> fetchErrorAction() },
shouldFetch = { true },
coroutineDispatcher = dispatchProvider.IO
).test {
// Assert that we've got the cached item
val cacheItem = awaitItem()
assertThat(cacheItem).isInstanceOf(Resource.Success::class.java)
val errorItem = awaitItem()
assertThat(errorItem).isInstanceOf(Resource.Error::class.java)
awaitComplete()
// Verify order & calls
verifyOrder {
fetchRequestAction()
fetchErrorAction()
}
verify(exactly = 1) { fetchErrorAction() }
verify(exactly = 1) { fetchRequestAction() }
verify(exactly = 0) { saveFetchResultAction() }
}
}
I want to display a loading indicator when I download data from the API. However, when this happens, the indicator often stops. How can I change this or what could be wrong? Basically, I fetch departure times and process them (E.g. I convert hex colors to Jetpack Compose color, or unix dates to Date type, etc.) and then load them into a list and display them.
#Composable
fun StopScreen(
unixDate: Long? = null,
stopId: String,
viewModel: MainViewModel = hiltViewModel()
) {
LaunchedEffect(Unit) {
viewModel.getArrivalsAndDeparturesForStop(
unixDate,
stopId,
false
)
}
val isLoading by remember { viewModel.isLoading }
if (!isLoading) {
//showData
} else {
LoadingView()
}
}
#Composable
fun LoadingView() {
Box(
contentAlignment = Alignment.Center,
modifier = Modifier.fillMaxSize()
) {
CircularProgressIndicator(color = MaterialTheme.colors.primary)
}
}
And the viewmodel where I process the data:
#HiltViewModel
class MainViewModel #Inject constructor(
private val mainRepository: MainRepository
) : ViewModel() {
var stopTimesList = mutableStateOf<MutableList<StopTime>>(arrayListOf())
var alertsList = mutableStateOf<MutableList<Alert>>(arrayListOf())
var loadError = mutableStateOf("")
var isLoading = mutableStateOf(false)
var isRefreshing = mutableStateOf(false)
fun getArrivalsAndDeparturesForStop(unixDate: Long? = null, stopId: String, refresh: Boolean) {
viewModelScope.launch {
if (refresh) {
isRefreshing.value = true
} else {
isLoading.value = true
}
val result = mainRepository.getArrivalsAndDeparturesForStop(stopId = stopId, time = unixDate)
when (result) {
is Resource.Success -> {
//I temporarily store the data here, so that the screen is only refreshed on reload when all the new data has arrived and loaded
var preStopTimes: MutableList<StopTime> = arrayListOf()
var preAlertsList: MutableList<Alert> = arrayListOf()
if (result.data!!.stopTimes != null && result.data!!.alerts != null) {
var count = 0
val countAll =
result.data!!.stopTimes!!.count() + result.data!!.alertIds!!.count()
if (countAll == 0) {
loadError.value = ""
isLoading.value = false
isRefreshing.value = false
}
//ALERTS
for (alert in result.data!!.data.alerts) {
preAlertsList.add(alert)
count += 1
if (count == countAll) {
stopTimesList.value = preStopTimes
alertsList.value = preAlertsList
loadError.value = ""
isLoading.value = false
isRefreshing.value = false
}
}
for (stopTime in result.data!!.stopTimes!!) {
preStopTimes.add(stopTime)
count += 1
if (count == countAll) {
stopTimesList.value = preStopTimes
alertsList.value = preAlertsList
loadError.value = ""
isLoading.value = false
isRefreshing.value = false
}
}
} else {
loadError.value = "Error"
isLoading.value = false
isRefreshing.value = false
}
}
is Resource.Error -> {
loadError.value = result.message!!
isLoading.value = false
isRefreshing.value = false
}
}
}
}
}
Repository:
#ActivityScoped
class MainRepository #Inject constructor(
private val api: MainApi
) {
suspend fun getArrivalsAndDeparturesForStop(stopId: String,time: Long? = null): Resource<ArrivalsAndDeparturesForStop> {
val response = try {
api.getArrivalsAndDeparturesForStop(
stopId,
time
)
} catch (e: Exception) { return Resource.Error(e.message!!)}
return Resource.Success(response)
}
}
My take is that your Composable recomposes way too often. Since you're updating your state within your for loops. Otherwise, it might be because your suspend method in your MainRepository is not dispatched in the right thread.
I feel you didn't yet grasp how Compose works internally (and that's fine, it's a new topic anyway). I'd recommend hoisting a unique state instead of having several mutable states for all your properties. Then build it internally in your VM to then notify the view when the state changes.
Something like this:
data class YourViewState(
val stopTimesList: List<StopTime> = emptyList(),
val alertsList: List<Alert> = emptyList(),
val isLoading: Boolean = false,
val isRefreshing: Boolean = false,
val loadError: String? = null,
)
#HiltViewModel
class MainViewModel #Inject constructor(
private val mainRepository: MainRepository
) : ViewModel() {
var viewState by mutableStateOf<YourViewState>(YourViewState())
fun getArrivalsAndDeparturesForStop(unixDate: Long? = null, stopId: String, refresh: Boolean) {
viewModelScope.launch {
viewState = if (refresh) {
viewState.copy(isRefreshing = true)
} else {
viewState.copy(isLoading = true)
}
when (val result = mainRepository.getArrivalsAndDeparturesForStop(stopId = stopId, time = unixDate)) {
is Resource.Success -> {
//I temporarily store the data here, so that the screen is only refreshed on reload when all the new data has arrived and loaded
val preStopTimes: MutableList<StopTime> = arrayListOf()
val preAlertsList: MutableList<Alert> = arrayListOf()
if (result.data!!.stopTimes != null && result.data!!.alerts != null) {
var count = 0
val countAll = result.data!!.stopTimes!!.count() + result.data!!.alertIds!!.count()
if (countAll == 0) {
viewState = viewState.copy(isLoading = false, isRefreshing = false)
}
//ALERTS
for (alert in result.data!!.data.alerts) {
preAlertsList.add(alert)
count += 1
if (count == countAll) {
break
}
}
for (stopTime in result.data!!.stopTimes!!) {
preStopTimes.add(stopTime)
count += 1
if (count == countAll) {
break
}
}
viewState = viewState.copy(isLoading = false, isRefreshing = false, stopTimesList = preStopTimes, alertsList = preAlertsList)
} else {
viewState = viewState.copy(isLoading = false, isRefreshing = false, loadError = "Error")
}
}
is Resource.Error -> {
viewState = viewState.copy(isLoading = false, isRefreshing = false, loadError = result.message!!)
}
}
}
}
}
#Composable
fun StopScreen(
unixDate: Long? = null,
stopId: String,
viewModel: MainViewModel = hiltViewModel()
) {
LaunchedEffect(Unit) {
viewModel.getArrivalsAndDeparturesForStop(
unixDate,
stopId,
false
)
}
if (viewModel.viewState.isLoading) {
LoadingView()
} else {
//showData
}
}
Note that I've made a few improvements while keeping the original structure.
EDIT:
You need to make your suspend method from your MainRepository main-safe. It's likely it runs on the main thread (caller thread) because you don't specify on which dispatcher the coroutine runs.
suspend fun getArrivalsAndDeparturesForStop(stopId: String,time: Long? = null): Resource<ArrivalsAndDeparturesForStop> = withContext(Dispatchers.IO) {
try {
api.getArrivalsAndDeparturesForStop(
stopId,
time
)
Resource.Success(response)
} catch (e: Exception) {
Resource.Error(e.message!!)
}
After 6 months I figured out the exact solution. Everything was running on the main thread when I processed the data in the ViewModel. Looking into things further, I should have used Dispatchers.Default and / or Dispatchers.IO within the functions for CPU intensive / list soring / JSON parsing tasks.
https://developer.android.com/kotlin/coroutines/coroutines-adv
suspend fun doSmg() {
withContext(Dispatchers.IO) {
//This dispatcher is optimized to perform disk or network I/O outside of the main thread. Examples include using the Room component, reading from or writing to files, and running any network operations.
}
withContext(Dispatchers.Default) {
//This dispatcher is optimized to perform CPU-intensive work outside of the main thread. Example use cases include sorting a list and parsing JSON.
}
}
I have a problem for now in JetpackCompose.
The problem is, when I'm collecting the Data from a flow, the value is getting fetched from firebase like there is a listener and the data's changing everytime. But tthat's not that.
I don't know what is the real problem!
FirebaseSrcNav
suspend fun getName(uid: String): Flow<Resource.Success<Any?>> = flow {
val query = userCollection.document(uid)
val snapshot = query.get().await().get("username")
emit(Resource.success(snapshot))
}
NavRepository
suspend fun getName(uid: String) = firebase.getName(uid)
HomeViewModel
fun getName(uid: String): MutableStateFlow<Any?> {
val name = MutableStateFlow<Any?>(null)
viewModelScope.launch {
navRepository.getName(uid).collect { nameState ->
when (nameState) {
is Resource.Success -> {
name.value = nameState.data
//_posts.value = state.data
loading.value = false
}
is Resource.Failure<*> -> {
Log.e(nameState.throwable, nameState.throwable)
}
}
}
}
return name
}
The probleme is in HomeScreen I think, when I'm calling the collectasState().value.
HomeScreen
val state = rememberLazyListState()
LazyColumn(
state = state,
verticalArrangement = Arrangement.spacedBy(10.dp)
) {
items(post) { post ->
//val difference = homeViewModel.getDateTime(homeViewModel.getTimestamp())
val date = homeViewModel.getDateTime(post.timeStamp!!)
val name = homeViewModel.getName(post.postAuthor_id.toString()).collectAsState().value
QuestionCard(
name = name.toString(),
date = date!!,
image = "",
text = post.postText!!,
like = 0,
response = 0,
topic = post.topic!!
)
}
}
I can't post video but if you need an image, imagine a textField where the test is alternating between "null" and "MyName" every 0.005 second.
Check official documentation.
https://developer.android.com/kotlin/flow
Flow is asynchronous
On viewModel
private val _name = MutableStateFlow<String>("")
val name: StateFlow<String>
get() = _name
fun getName(uid: String) {
viewModelScope.launch {
//asyn call
navRepository.getName(uid).collect { nameState ->
when (nameState) {
is Resource.Success -> {
name.value = nameState.data
}
is Resource.Failure<*> -> {
//manager error
Log.e(nameState.throwable, nameState.throwable)
}
}
}
}
}
on your view
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
...
lifecycleScope.launch {
viewModel.name.collect { name -> handlename
}
}
}
I know that there are a lot of posts "How to cancel Coroutines Scope" but I couldn't find the answer for my case.
I have an Array of objects that I want to send each of them to Server using Coroutines.
What I need is, if one of my requests returns error, canceling others.
Here is my code:
private fun sendDataToServer(function: () -> Unit) {
LiabilitiesWizardSessionManager.getLiabilityAddedDocuments().let { documents ->
if (documents.isEmpty().not()) {
CoroutineScope(Dispatchers.IO).launch {
documents.mapIndexed { index, docDetail ->
async {
val result = uploadFiles(docDetail)
}
}.map {
var result = it.await()
}
}
} else function.invoke()
}
}
Below is my uploadFiles() function:
private suspend fun uploadFiles(docDetail: DocDetail): ArchiveFileResponse? {
LiabilitiesWizardSessionManager.mCreateLiabilityModel.let { model ->
val file = File(docDetail.fullFilePath)
val crmCode = docDetail.docTypeCode
val desc = docDetail.docTypeDesc
val id = model.commitmentMember?.id
val idType = 1
val createArchiveFileModel = CreateArchiveFileModel(108, desc, id, idType).apply {
this.isLiability = true
this.adaSystem = 3
}
val result = mRepositoryControllerKotlin.uploadFile(file, createArchiveFileModel)
return when (result) {
is ResultWrapper.Success -> {
result.value
}
is ResultWrapper.GenericError -> {
null
}
is ResultWrapper.NetworkError -> {
null
}
}
}
}
I know, I'm missing something.
I am using kotlin coroutines for network request using extension method to call class in retrofit like this
public suspend fun <T : Any> Call<T>.await(): T {
return suspendCancellableCoroutine { continuation ->
enqueue(object : Callback<T> {
override fun onResponse(call: Call<T>?, response: Response<T?>) {
if (response.isSuccessful) {
val body = response.body()
if (body == null) {
continuation.resumeWithException(
NullPointerException("Response body is null")
)
} else {
continuation.resume(body)
}
} else {
continuation.resumeWithException(HttpException(response))
}
}
override fun onFailure(call: Call<T>, t: Throwable) {
// Don't bother with resuming the continuation if it is already cancelled.
if (continuation.isCancelled) return
continuation.resumeWithException(t)
}
})
registerOnCompletion(continuation)
}
}
then from calling side i am using above method like this
private fun getArticles() = launch(UI) {
loading.value = true
try {
val networkResult = api.getArticle().await()
articles.value = networkResult
}catch (e: Throwable){
e.printStackTrace()
message.value = e.message
}finally {
loading.value = false
}
}
i want to exponential retry this api call in some case i.e (IOException) how can i achieve it ??
I would suggest to write a helper higher-order function for your retry logic. You can use the following implementation for a start:
suspend fun <T> retryIO(
times: Int = Int.MAX_VALUE,
initialDelay: Long = 100, // 0.1 second
maxDelay: Long = 1000, // 1 second
factor: Double = 2.0,
block: suspend () -> T): T
{
var currentDelay = initialDelay
repeat(times - 1) {
try {
return block()
} catch (e: IOException) {
// you can log an error here and/or make a more finer-grained
// analysis of the cause to see if retry is needed
}
delay(currentDelay)
currentDelay = (currentDelay * factor).toLong().coerceAtMost(maxDelay)
}
return block() // last attempt
}
Using this function is very strightforward:
val networkResult = retryIO { api.getArticle().await() }
You can change retry parameters on case-by-case basis, for example:
val networkResult = retryIO(times = 3) { api.doSomething().await() }
You can also completely change the implementation of retryIO to suit the needs of your application. For example, you can hard-code all the retry parameters, get rid of the limit on the number of retries, change defaults, etc.
Here an example with the Flow and the retryWhen function
RetryWhen Extension :
fun <T> Flow<T>.retryWhen(
#FloatRange(from = 0.0) initialDelay: Float = RETRY_INITIAL_DELAY,
#FloatRange(from = 1.0) retryFactor: Float = RETRY_FACTOR_DELAY,
predicate: suspend FlowCollector<T>.(cause: Throwable, attempt: Long, delay: Long) -> Boolean
): Flow<T> = this.retryWhen { cause, attempt ->
val retryDelay = initialDelay * retryFactor.pow(attempt.toFloat())
predicate(cause, attempt, retryDelay.toLong())
}
Usage :
flow {
...
}.retryWhen { cause, attempt, delay ->
delay(delay)
...
}
Here's a more sophisticated and convenient version of my previous answer, hope it helps someone:
class RetryOperation internal constructor(
private val retries: Int,
private val initialIntervalMilli: Long = 1000,
private val retryStrategy: RetryStrategy = RetryStrategy.LINEAR,
private val retry: suspend RetryOperation.() -> Unit
) {
var tryNumber: Int = 0
internal set
suspend fun operationFailed() {
tryNumber++
if (tryNumber < retries) {
delay(calculateDelay(tryNumber, initialIntervalMilli, retryStrategy))
retry.invoke(this)
}
}
}
enum class RetryStrategy {
CONSTANT, LINEAR, EXPONENTIAL
}
suspend fun retryOperation(
retries: Int = 100,
initialDelay: Long = 0,
initialIntervalMilli: Long = 1000,
retryStrategy: RetryStrategy = RetryStrategy.LINEAR,
operation: suspend RetryOperation.() -> Unit
) {
val retryOperation = RetryOperation(
retries,
initialIntervalMilli,
retryStrategy,
operation,
)
delay(initialDelay)
operation.invoke(retryOperation)
}
internal fun calculateDelay(tryNumber: Int, initialIntervalMilli: Long, retryStrategy: RetryStrategy): Long {
return when (retryStrategy) {
RetryStrategy.CONSTANT -> initialIntervalMilli
RetryStrategy.LINEAR -> initialIntervalMilli * tryNumber
RetryStrategy.EXPONENTIAL -> 2.0.pow(tryNumber).toLong()
}
}
Usage:
coroutineScope.launch {
retryOperation(3) {
if (!tryStuff()) {
Log.d(TAG, "Try number $tryNumber")
operationFailed()
}
}
}
Flow Version https://github.com/hoc081098/FlowExt
package com.hoc081098.flowext
import kotlin.time.Duration
import kotlin.time.ExperimentalTime
import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.FlowCollector
import kotlinx.coroutines.flow.emitAll
import kotlinx.coroutines.flow.flow
import kotlinx.coroutines.flow.retryWhen
#ExperimentalTime
public fun <T> Flow<T>.retryWithExponentialBackoff(
initialDelay: Duration,
factor: Double,
maxAttempt: Long = Long.MAX_VALUE,
maxDelay: Duration = Duration.INFINITE,
predicate: suspend (cause: Throwable) -> Boolean = { true }
): Flow<T> {
require(maxAttempt > 0) { "Expected positive amount of maxAttempt, but had $maxAttempt" }
return retryWhenWithExponentialBackoff(
initialDelay = initialDelay,
factor = factor,
maxDelay = maxDelay
) { cause, attempt -> attempt < maxAttempt && predicate(cause) }
}
#ExperimentalTime
public fun <T> Flow<T>.retryWhenWithExponentialBackoff(
initialDelay: Duration,
factor: Double,
maxDelay: Duration = Duration.INFINITE,
predicate: suspend FlowCollector<T>.(cause: Throwable, attempt: Long) -> Boolean
): Flow<T> = flow {
var currentDelay = initialDelay
retryWhen { cause, attempt ->
predicate(cause, attempt).also {
if (it) {
delay(currentDelay)
currentDelay = (currentDelay * factor).coerceAtMost(maxDelay)
}
}
}.let { emitAll(it) }
}
You can try this simple but very agile approach with simple usage:
EDIT: added a more sophisticated solution in a separate answer.
class Completion(private val retry: (Completion) -> Unit) {
fun operationFailed() {
retry.invoke(this)
}
}
fun retryOperation(retries: Int,
dispatcher: CoroutineDispatcher = Dispatchers.Default,
operation: Completion.() -> Unit
) {
var tryNumber = 0
val completion = Completion {
tryNumber++
if (tryNumber < retries) {
GlobalScope.launch(dispatcher) {
delay(TimeUnit.SECONDS.toMillis(tryNumber.toLong()))
operation.invoke(it)
}
}
}
operation.invoke(completion)
}
The use it like this:
retryOperation(3) {
if (!tryStuff()) {
// this will trigger a retry after tryNumber seconds
operationFailed()
}
}
You can obviously build more on top of it.