Trip into the async world @ NYC Kotlin Meetup

Transcript

1. Trip into the async world

2. Rob

3. Why RxJava?

4. Why RxJava? Retrofit

5. Why RxJava? Retrofit Async ops

6. Why RxJava? Retrofit Async ops Basic operators

7. Why RxJava? Retrofit Async ops Basic operators Advanced operators

8. Why RxJava? Retrofit Async ops Basic operators Advanced operators

9. Why RxJava? Retrofit Async ops Basic operators Advanced operators

10. implementation ‘com.squareup.retrofit2:retrofit:2.6.1’

11. @GET("/path/to/resource") fun networkRequest(): Single<Data> @GET("/path/to/resource") suspend fun networkRequest(): Data

12. Retrofit.Builder() ... .addCallAdapterFactory(CoroutineCallAdapterFactory()) .addCallAdapterFactory(RxJava2CallAdapterFactory.create()) .build()

13. CoroutineCallAdapterFactory() RxJava2CallAdapterFactory.create()

14. @Test fun test() { runBlocking { val response = api.networkRequest()

    assertThat(response)... } api.networkRequest() .test() .assertValue { } }
15. None

16. 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() } }

17. 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

18. 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

19. 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)) } } } }

20. 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)) } } } }

21. 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)) } }

22. map flatmap filter first last

23. map flatmap filter first last forEach orEmpty mapNotNull

24. @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(); } } }); } }); }

25. @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() } }

26. 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() } }

27. val job = Job() val scope = CoroutineScope(Dispatchers.IO + job)

    fun doThings() { scope.launch { ... } } fun inTheEnd() { job.cancel() }

28. val job = Job() val scope = CoroutineScope(Dispatchers.IO + job)

    fun doThings() { scope.launch { ... } } fun inTheEnd() { job.cancelChildren() scope.coroutineContext.cancelChildren() }

29. 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) } }
30. None

31. kotlinx-coroutines-rx2

32. class RxThing { fun doStuff() : Single<MyData> }

33. suspend fun doThings() { val my data = rxThing.doStuff().await() }

34. class CoroutineThing { suspend fun doStuff() : MyData }

35. fun doStuff() : Single<MyData> = rxSingle { coroutineThing.doStuff() }

36. fun doStuff() : Single<MyData> = rxSingle(RxCoroutineExceptionHandler) { coroutineThing.doStuff() }

37. None

38. open.nytimes.com @nytdev github.com/NYTimes developers.nytimes.com

39. QA &