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Trip into the async world @ NYC Kotlin Meetup
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Roberto Orgiu
October 16, 2019
Programming
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66
Trip into the async world @ NYC Kotlin Meetup
These are the slides of my talk from NYC Kotlin Meetup @ Dropbox
Roberto Orgiu
October 16, 2019
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Transcript
Trip into the async world
Rob
Why RxJava?
Why RxJava? Retrofit
Why RxJava? Retrofit Async ops
Why RxJava? Retrofit Async ops Basic operators
Why RxJava? Retrofit Async ops Basic operators Advanced operators
Why RxJava? Retrofit Async ops Basic operators Advanced operators
Why RxJava? Retrofit Async ops Basic operators Advanced operators
implementation ‘com.squareup.retrofit2:retrofit:2.6.1’
@GET("/path/to/resource") fun networkRequest(): Single<Data> @GET("/path/to/resource") suspend fun networkRequest(): Data
Retrofit.Builder() ... .addCallAdapterFactory(CoroutineCallAdapterFactory()) .addCallAdapterFactory(RxJava2CallAdapterFactory.create()) .build()
CoroutineCallAdapterFactory() RxJava2CallAdapterFactory.create()
@Test fun test() { runBlocking { val response = api.networkRequest()
assertThat(response)... } api.networkRequest() .test() .assertValue { } }
None
class DataViewModel()) : ViewModel() { private val subscriptions = CompositeDisposable()
val output = BehaviorSubject<LCE<Data>>.create() fun loadCurrentStatus() { disposable += store.get(BarCode.empty()) .startWith(LceLoading()) .onErrorReturn({e -> LceError(e)}) .map({data -> mapEmptyData(data)}) .observeOn(AndroidSchedulers.mainThread()) .subscribeOn(Schedulers.io()) .subscribe(output) } override fun onCleared() { disposable.clear() } }
class DataViewModel()) : ViewModel() { private val subscriptions = CompositeDisposable()
val output = BehaviorSubject<LCE<Data>>.create() fun loadCurrentStatus() { disposable += store.get(BarCode.empty()) .startWith(LceLoading()) .onErrorReturn({e -> LceError(e)}) .map({data -> mapEmptyData(data)}) .observeOn(AndroidSchedulers.mainThread()) .subscribeOn(Schedulers.io()) .subscribe(output) } override fun onCleared() { disposable.clear() } } Hidden knowledge
te val subscriptions = CompositeDisposable() utput = BehaviorSubject<LCE<Data>>.create() oadCurrentStatus() {
isposable += store.get(BarCode.empty()) .startWith(LceLoading()) .onErrorReturn({e -> LceError(e)}) .map({data -> mapEmptyData(data)}) .observeOn(AndroidSchedulers.mainThread()) .subscribeOn(Schedulers.io()) .subscribe(output) ide fun onCleared() { isposable.clear() Learning curve
class DataViewModel()) : ViewModel() { val output = MutableLiveData<Data>() fun
loadCurrentStatus() { output.postValue(LceLoading()) viewModelScope.launch { try { val data = store.get(BarCode.empty()).await() if (data.isEmpty()) { output.postValue(LceError(EmptyResultSetException())) } else { output.postValue(LceSuccess(data)) } } catch (e: Exception) { output.postValue(LceError(e)) } } } }
class DataViewModel()) : ViewModel() { val output = MutableLiveData<Data>() fun
loadCurrentStatus() { output.postValue(LceLoading()) viewModelScope.launch { try { val data = store.get(BarCode.empty()).await() if (data.isEmpty()) { output.postValue(LceError(EmptyResultSetException())) } else { output.postValue(LceSuccess(data)) } } catch (e: Exception) { output.postValue(LceError(e)) } } } }
adCurrentStatus() { output.postValue(LceLoading()) viewModelScope.launch { try { val data =
store.get(BarCode.empty()).await() if (data.isEmpty()) { output.postValue(LceError(EmptyResultSetException())) } else { output.postValue(LceSuccess(data)) } } catch (e: Exception) { output.postValue(LceError(e)) } }
map flatmap filter first last
map flatmap filter first last forEach orEmpty mapNotNull
@NotNull public static <T> Observable<Response<T>> from(@NotNull final ApolloCall<T> call) {
checkNotNull(call, "call == null"); return Observable.create(new ObservableOnSubscribe<Response<T>>() { @Override public void subscribe(final ObservableEmitter<Response<T>> emitter) throws Exception { cancelOnObservableDisposed(emitter, call); call.enqueue(new ApolloCall.Callback<T>() { @Override public void onResponse(@NotNull Response<T> response) { if (!emitter.isDisposed()) { emitter.onNext(response); } } @Override public void onFailure(@NotNull ApolloException e) { Exceptions.throwIfFatal(e); if (!emitter.isDisposed()) { emitter.onError(e); } } @Override public void onStatusEvent(@NotNull ApolloCall.StatusEvent event) { if (event == ApolloCall.StatusEvent.COMPLETED && !emitter.isDisposed()) { emitter.onComplete(); } } }); } }); }
@NotNull public static <T> Observable<Response<T>> from(@NotNull final ApolloCall<T> call) {
checkNotNull(call, "call == null"); return Observable.create(new ObservableOnSubscribe<Response<T>>() { @Override public void subscribe(final ObservableEmitter<Response<T>> emitter) throws Exception { cancelOnObservableDisposed(emitter, call); call.enqueue(new ApolloCall.Callback<T>() { @Override public void onResponse(@NotNull Response<T> response) { if (!emitter.isDisposed()) { emitter.onNext(response); } } @Override public void onFailure(@NotNull ApolloException e) { Exceptions.throwIfFatal(e); if (!emitter.isDisposed()) { emitter.onError(e); } } @Override public void onStatusEvent(@NotNull ApolloCall.StatusEvent event) { if (event == ApolloCall.StatusEvent.COMPLETED && !emitter.isDisposed()) { emitter.onComplete(); } } }); } }); } suspend fun <T> ApolloCall<T>.await(): Response<T> = suspendCancellableCoroutine { cont -> enqueue(object : ApolloCall.Callback<T>() { override fun onFailure(e: ApolloException) { cont.resumeWithException(e) } override fun onResponse(response: Response<T>) { cont.resume(response) } }) cont.invokeOnCancellation { cancel() } }
suspend fun <T> ApolloCall<T>.await(): Response<T> = suspendCancellableCoroutine { cont ->
enqueue(object : ApolloCall.Callback<T>() { override fun onFailure(e: ApolloException) { cont.resumeWithException(e) } override fun onResponse(response: Response<T>) { cont.resume(response) } }) cont.invokeOnCancellation { cancel() } }
val job = Job() val scope = CoroutineScope(Dispatchers.IO + job)
fun doThings() { scope.launch { ... } } fun inTheEnd() { job.cancel() }
val job = Job() val scope = CoroutineScope(Dispatchers.IO + job)
fun doThings() { scope.launch { ... } } fun inTheEnd() { job.cancelChildren() scope.coroutineContext.cancelChildren() }
job.cancelChildren() scope.coroutineContext.cancelChildren() public fun Job.cancelChildren(cause: CancellationException? = null) { children.forEach
{ it.cancel(cause) } } public fun CoroutineContext.cancelChildren(cause: CancellationException? = null) { this[Job]?.children?.forEach { it.cancel(cause) } }
None
kotlinx-coroutines-rx2
class RxThing { fun doStuff() : Single<MyData> }
suspend fun doThings() { val my data = rxThing.doStuff().await() }
class CoroutineThing { suspend fun doStuff() : MyData }
fun doStuff() : Single<MyData> = rxSingle { coroutineThing.doStuff() }
fun doStuff() : Single<MyData> = rxSingle(RxCoroutineExceptionHandler) { coroutineThing.doStuff() }
None
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