Trip into the async world

This deck is the base of the presentation about migrating from RxJava to Coroutines I gave at Conference for Kotliners, in Budapest

Transcript

1. Trip into the
   async world
   

   View Slide

2. Rob
   

   View Slide

3. Why RxJava?
   

   View Slide

4. Why RxJava?
   Retrofit
   

   View Slide

5. Why RxJava?
   Retrofit
   Async ops
   

   View Slide

6. Why RxJava?
   Retrofit
   Async ops
   Basic operators
   

   View Slide

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

   View Slide

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

   View Slide

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

   View Slide

10. implementation
    'com.squareup.retrofit2:retrofit:2.6.0’
    

    View Slide

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

    View Slide

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

    View Slide

13. CoroutineCallAdapterFactory()
    RxJava2CallAdapterFactory.create()
    

    View Slide

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

    View Slide

15. View Slide

16. class DataViewModel()) : ViewModel() {
    private val subscriptions = CompositeDisposable()
    val output = BehaviorSubject>.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()
    }
    }
    

    View Slide

17. class DataViewModel()) : ViewModel() {
    private val subscriptions = CompositeDisposable()
    val output = BehaviorSubject>.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
    

    View Slide

18. te val subscriptions = CompositeDisposable()
    utput = BehaviorSubject>.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
    

    View Slide

19. class DataViewModel()) : ViewModel() {
    val output = MutableLiveData()
    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))
    }
    }
    }
    }
    

    View Slide

20. class DataViewModel()) : ViewModel() {
    val output = MutableLiveData()
    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))
    }
    }
    }
    }
    

    View Slide

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))
    }
    }
    

    View Slide

22. map
    flatmap
    filter
    first
    last
    

    View Slide

23. map
    flatmap
    filter
    first
    last
    forEach
    orEmptyT
    mapNotNull
    

    View Slide

24. @NotNull public static Observable> from(@NotNull final ApolloCall call) {
    checkNotNull(call, "call == null");
    return Observable.create(new ObservableOnSubscribe>() {
    @Override public void subscribe(final ObservableEmitter> emitter) throws Exception {
    cancelOnObservableDisposed(emitter, call);
    call.enqueue(new ApolloCall.Callback() {
    @Override public void onResponse(@NotNull Response 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();
    }
    }
    });
    }
    });
    }
    

    View Slide

25. @NotNull public static Observable> from(@NotNull final ApolloCall call) {
    checkNotNull(call, "call == null");
    return Observable.create(new ObservableOnSubscribe>() {
    @Override public void subscribe(final ObservableEmitter> emitter) throws Exception {
    cancelOnObservableDisposed(emitter, call);
    call.enqueue(new ApolloCall.Callback() {
    @Override public void onResponse(@NotNull Response 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 ApolloCall.await(): Response =
    suspendCancellableCoroutine { cont ->
    enqueue(object : ApolloCall.Callback() {
    override fun onFailure(e: ApolloException) {
    cont.resumeWithException(e)
    }
    override fun onResponse(response: Response) {
    cont.resume(response)
    }
    })
    cont.invokeOnCancellation { cancel() }
    }
    

    View Slide

26. suspend fun ApolloCall.await(): Response =
    suspendCancellableCoroutine { cont ->
    enqueue(object : ApolloCall.Callback() {
    override fun onFailure(e: ApolloException) {
    cont.resumeWithException(e)
    }
    override fun onResponse(response: Response) {
    cont.resume(response)
    }
    })
    cont.invokeOnCancellation { cancel() }
    }
    

    View Slide

27. val job = Job()
    val scope = CoroutineScope(Dispatchers.IO + job)
    fun doThings() {
    scope.launch {
    ...
    }
    }
    fun inTheEnd() {
    job.cancel()
    }
    

    View Slide

28. val job = Job()
    val scope = CoroutineScope(Dispatchers.IO + job)
    fun doThings() {
    scope.launch {
    ...
    }
    }
    fun inTheEnd() {
    job.cancelChildren()
    scope.coroutineContext.cancelChildren()
    }
    

    View Slide

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) }
    }
    

    View Slide

30. View Slide

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

    View Slide

32. QA
    &
    

    View Slide