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Demystifying RxJava Subscribers Jake Wharton

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Reactive Streams

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Reactive Streams 1 2 3 4 5 6

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Reactive Streams 1 2 3 4 5 6 [ ]

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Reactive Streams 1 2 3 4 5 6 [ ] for ( in i )

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Reactive Streams 1 2 3 4 5 6 [ ] for ( in i ) scale( ) i

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Reactive Streams 1 2 3 4 5 6 [ ] for ( in i ) if ( % 2 == 0) i scale( ) i

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Reactive Streams

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Reactive Streams 1 2 3 4 5 6

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Reactive Streams 1 2 3 4 5 6

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Reactive Streams

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Reactive Streams filter( % 2 == 0) i

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Reactive Streams filter( % 2 == 0) i

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Reactive Streams 1 2 3 4 5 6 2 4 6 filter( % 2 == 0) i

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Reactive Streams 1 2 3 4 5 6

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Observable.just( , , , , , ) Reactive Streams 1 2 3 4 5 6

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Observable.just( , , , , , ) Reactive Streams 1 2 3 4 5 6 .filter( -> % 2 == 0) i i

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Observable.just( , , , , , ) Reactive Streams 1 2 3 4 5 6 .filter( -> % 2 == 0) i i .subscribe( -> { }); i 2 4 6

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Observable.just(1, 2, 3, 4, 5, 6)
 .filter(i -> i % 2 == 0)
 .subscribe(new Action1() {
 @Override public void call(Integer item) {
 System.out.println(item);
 }
 }); Reactive Streams -> i i i

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Subscribers?

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Subscribers? interface Observer {
 void onNext(T item);
 void onCompleted();
 void onError(Throwable t);
 }

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Subscribers? interface Observer {
 void onNext(T item);
 void onCompleted();
 void onError(Throwable t);
 } interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }

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Subscribers? interface Action1 {
 void call(T t);
 } interface Observer {
 void onNext(T item);
 void onCompleted();
 void onError(Throwable t);
 } interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }

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Subscribers? interface Action1 {
 void call(T t);
 } // ...and friends! interface Observer {
 void onNext(T item);
 void onCompleted();
 void onError(Throwable t);
 } interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }

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Subscribers? interface Action1 {
 void call(T t);
 } // ...and friends! interface Func1 {
 R call(T t);
 } interface Observer {
 void onNext(T item);
 void onCompleted();
 void onError(Throwable t);
 } interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }

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Subscribers? interface Action1 {
 void call(T t);
 } // ...and friends! interface Func1 {
 R call(T t);
 }
 // ...and friends! interface Observer {
 void onNext(T item);
 void onCompleted();
 void onError(Throwable t);
 } interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }

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Subscribers? interface Action1 {
 void call(T t);
 }X // ...and friends! interface Func1 {
 R call(T t);
 }X
 // ...and friends! interface Observer {
 void onNext(T item);
 void onCompleted();
 void onError(Throwable t);
 }X interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }X class Observable {
 static Observable create(OnSubscribe f);
 Observable lift(Operator operator);
 Observable compose(Transformer transformer);
 static Observable amb(Iterable> sources);
 static Observable amb(Observable o1, Observable o2);
 static Observable amb(Observable o1, Observable o2, Observable o3);
 static Observable amb(Observable o1, Observable o2, Observable o3, Observable o4);
 static Observable amb(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5);
 static Observable amb(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6);
 static Observable amb(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6, Observable o7);
 static Observable amb(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6, Observable o7, Observable o8);
 static Observable amb(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6, Observable o7, Observable o8, Observable o9);
 static Observable combineLatest(Observable o1, Observable o2, Func2 combineFunction);
 static Observable combineLatest(Observable o1, Observable o2, Observable o3, Func3 combineFunction);
 static Observable combineLatest(Observable o1, Observable o2, Observable o3, Observable o4, Func4 combineFunction);
 static Observable combineLatest(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Func5 combineFunction);
 static Observable combineLatest(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6, Func6 Observable combineLatest(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6, Observable o7, Func7 Observable combineLatest(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6, Observable o7, Observable o8, Func8 Observable combineLatest(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6, Observable o7, Observable o8, Observable static Observable combineLatest(List> sources, FuncN combineFunction);
 static Observable concat(Observable> observables);
 static Observable concat(Observable t1, Observable t2);
 static Observable concat(Observable t1, Observable t2, Observable t3);
 static Observable concat(Observable t1, Observable t2, Observable t3, Observable t4);
 static Observable concat(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5);
 static Observable concat(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6);
 static Observable concat(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6, Observable t7);
 static Observable concat(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6, Observable t7, Observable t8);
 static Observable concat(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6, Observable t7, Observable t8, Observable t9);
 static Observable defer(Func0> observableFactory);
 static Observable empty();
 static Observable error(Throwable exception);
 static Observable from(Future future);
 static Observable from(Future future, long timeout, TimeUnit unit);
 static Observable from(Future future, Scheduler scheduler);
 static Observable from(Iterable iterable);
 static Observable from(T[] array);
 static Observable interval(long interval, TimeUnit unit);
 static Observable interval(long interval, TimeUnit unit, Scheduler scheduler);
 static Observable interval(long initialDelay, long period, TimeUnit unit);
 static Observable interval(long initialDelay, long period, TimeUnit unit, Scheduler scheduler);
 static Observable just(T value);
 static Observable just(T t1, T t2);
 static Observable just(T t1, T t2, T t3);
 static Observable just(T t1, T t2, T t3, T t4);
 static Observable just(T t1, T t2, T t3, T t4, T t5);
 static Observable just(T t1, T t2, T t3, T t4, T t5, T t6);
 static Observable just(T t1, T t2, T t3, T t4, T t5, T t6, T t7);
 static Observable just(T t1, T t2, T t3, T t4, T t5, T t6, T t7, T t8);
 static Observable just(T t1, T t2, T t3, T t4, T t5, T t6, T t7, T t8, T t9);
 static Observable just(T t1, T t2, T t3, T t4, T t5, T t6, T t7, T t8, T t9, T t10);
 static Observable merge(Iterable> sequences);
 static Observable merge(Iterable> sequences, int maxConcurrent);
 static Observable merge(Observable> source);
 static Observable merge(Observable> source, int maxConcurrent);
 static Observable merge(Observable t1, Observable t2);
 static Observable merge(Observable t1, Observable t2, Observable t3);
 static Observable merge(Observable t1, Observable t2, Observable t3, Observable t4);
 static Observable merge(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5);
 static Observable merge(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6);
 static Observable merge(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6, Observable t7);
 static Observable merge(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6, Observable t7, Observable t8);
 static Observable merge(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6, Observable t7, Observable t8, Observable t9);
 static Observable merge(Observable[] sequences);
 static Observable merge(Observable[] sequences, int maxConcurrent);
 static Observable mergeDelayError(Observable> source);
 static Observable mergeDelayError(Observable> source, int maxConcurrent);
 static Observable mergeDelayError(Observable t1, Observable t2);
 static Observable mergeDelayError(Observable t1, Observable t2, Observable t3);
 static Observable mergeDelayError(Observable t1, Observable t2, Observable t3, Observable t4);
 static Observable mergeDelayError(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5);
 static Observable mergeDelayError(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6);
 static Observable mergeDelayError(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6, Observable t7);
 static Observable mergeDelayError(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6, Observable t7, Observable t8);
 static Observable mergeDelayError(Observable t1, Observable t2, Observable t3, Observable t4, Observable t5, Observable t6, Observable t7, Observable t8, Observable t9);
 Observable> nest();
 static Observable never();
 static Observable range(int start, int count);
 static Observable range(int start, int count, Scheduler scheduler);
 static Observable sequenceEqual(Observable first, Observable second);
 static Observable sequenceEqual(Observable first, Observable second, Func2 equality);
 static Observable switchOnNext(Observable> sequenceOfSequences);
 static Observable timer(long delay, TimeUnit unit);
 static Observable timer(long delay, TimeUnit unit, Scheduler scheduler);
 static Observable using(Func0 resourceFactory, Func1> observableFactory, Action1 disposeAction);
 static Observable using(Func0 resourceFactory, Func1> observableFactory, Action1 disposeAction, boolean disposeEagerly);
 static Observable zip(Iterable> ws, FuncN zipFunction);
 static Observable zip(Observable> ws, FuncN zipFunction);
 static Observable zip(Observable o1, Observable o2, Func2 zipFunction);
 static Observable zip(Observable o1, Observable o2, Observable o3, Func3 zipFunction);
 static Observable zip(Observable o1, Observable o2, Observable o3, Observable o4, Func4 zipFunction);
 static Observable zip(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Func5 zipFunction);
 static Observable zip(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6, Func6 static Observable zip(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6, Observable o7, Func7 Observable zip(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6, Observable o7, Observable o8, Func8 Observable zip(Observable o1, Observable o2, Observable o3, Observable o4, Observable o5, Observable o6, Observable o7, Observable o8, Observable

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Subscribers? interface Action1 {
 void call(T t);
 }X // ...and friends! interface Func1 {
 R call(T t);
 }X
 // ...and friends! interface Observer {
 void onNext(T item);
 void onCompleted();
 void onError(Throwable t);
 }X interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }X Observable share();
 Observable single();
 Observable single(Func1 predicate);
 Observable singleOrDefault(T defaultValue);
 Observable singleOrDefault(T defaultValue, Func1 predicate);
 Observable skip(int count);
 Observable skip(long time, TimeUnit unit);
 Observable skip(long time, TimeUnit unit, Scheduler scheduler);
 Observable skipLast(int count);
 Observable skipLast(long time, TimeUnit unit);
 Observable skipLast(long time, TimeUnit unit, Scheduler scheduler);
 Observable skipUntil(Observable other);
 Observable skipWhile(Func1 predicate);
 Observable startWith(Observable values);
 Observable startWith(Iterable values);
 Observable startWith(T t1);
 Observable startWith(T t1, T t2);
 Observable startWith(T t1, T t2, T t3);
 Observable startWith(T t1, T t2, T t3, T t4);
 Observable startWith(T t1, T t2, T t3, T t4, T t5);
 Observable startWith(T t1, T t2, T t3, T t4, T t5, T t6);
 Observable startWith(T t1, T t2, T t3, T t4, T t5, T t6, T t7);
 Observable startWith(T t1, T t2, T t3, T t4, T t5, T t6, T t7, T t8);
 Observable startWith(T t1, T t2, T t3, T t4, T t5, T t6, T t7, T t8, T t9);
 Subscription subscribe();
 Subscription subscribe(Action1 onNext);
 Subscription subscribe(Action1 onNext, Action1 onError);
 Subscription subscribe(Action1 onNext, Action1 onError, Action0 onComplete);
 Subscription subscribe(Observer observer);
 Subscription unsafeSubscribe(Subscriber subscriber);
 Subscription subscribe(Subscriber subscriber);
 Observable subscribeOn(Scheduler scheduler);
 Observable switchMap(Func1> func);
 Observable take(int count);
 Observable take(long time, TimeUnit unit);
 Observable take(long time, TimeUnit unit, Scheduler scheduler);
 Observable takeFirst(Func1 predicate);
 Observable takeLast(int count);
 Observable takeLast(int count, long time, TimeUnit unit);
 Observable takeLast(int count, long time, TimeUnit unit, Scheduler scheduler);
 Observable takeLast(long time, TimeUnit unit);
 Observable takeLast(long time, TimeUnit unit, Scheduler scheduler);
 Observable> takeLastBuffer(int count);
 Observable> takeLastBuffer(int count, long time, TimeUnit unit);
 Observable> takeLastBuffer(int count, long time, TimeUnit unit, Scheduler scheduler);
 Observable> takeLastBuffer(long time, TimeUnit unit);
 Observable> takeLastBuffer(long time, TimeUnit unit, Scheduler scheduler);
 Observable takeUntil(Observable other);
 Observable takeWhile(Func1 predicate);
 Observable takeUntil(Func1 stopPredicate);
 Observable throttleFirst(long windowDuration, TimeUnit unit);
 Observable throttleFirst(long skipDuration, TimeUnit unit, Scheduler scheduler);
 Observable throttleLast(long intervalDuration, TimeUnit unit);
 Observable throttleLast(long intervalDuration, TimeUnit unit, Scheduler scheduler);
 Observable throttleWithTimeout(long timeout, TimeUnit unit);
 Observable throttleWithTimeout(long timeout, TimeUnit unit, Scheduler scheduler);
 Observable> timeInterval();
 Observable> timeInterval(Scheduler scheduler);
 Observable timeout(Func0> firstTimeoutSelector, Func1> timeoutSelector);
 Observable timeout(Func0> firstTimeoutSelector, Func1> timeoutSelector, Observable other);
 Observable timeout(Func1> timeoutSelector);
 Observable timeout(Func1> timeoutSelector, Observable other);
 Observable timeout(long timeout, TimeUnit timeUnit);
 Observable timeout(long timeout, TimeUnit timeUnit, Observable other);
 Observable timeout(long timeout, TimeUnit timeUnit, Observable other, Scheduler scheduler);
 Observable timeout(long timeout, TimeUnit timeUnit, Scheduler scheduler);
 Observable> timestamp();
 Observable> timestamp(Scheduler scheduler);
 BlockingObservable toBlocking();
 Observable> toList();
 Observable> toMap(Func1 keySelector);
 Observable> toMap(Func1 keySelector, Func1 valueSelector);
 Observable> toMap(Func1 keySelector, Func1 valueSelector, Func0> mapFactory);
 Observable>> toMultimap(Func1 keySelector);
 Observable>> toMultimap(Func1 keySelector, Func1 valueSelector);
 Observable>> toMultimap(Func1 keySelector, Func1 valueSelector, Func0>> mapFactory);
 Observable>> toMultimap(Func1 keySelector, Func1 valueSelector, Func0>> mapFactory, Func1> collectionFactory);
 Observable> toSortedList();
 Observable> toSortedList(Func2 sortFunction);
 Observable> toSortedList(int initialCapacity);
 Observable> toSortedList(Func2 sortFunction, int initialCapacity);
 Observable unsubscribeOn(Scheduler scheduler);
 Observable withLatestFrom(Observable other, Func2 resultSelector);
 Observable> window(Func0> closingSelector);
 Observable> window(int count);
 Observable> window(int count, int skip);
 Observable> window(long timespan, long timeshift, TimeUnit unit);
 Observable> window(long timespan, long timeshift, TimeUnit unit, Scheduler scheduler);
 Observable> window(long timespan, long timeshift, TimeUnit unit, int count, Scheduler scheduler);
 Observable> window(long timespan, TimeUnit unit);
 Observable> window(long timespan, TimeUnit unit, int count);
 Observable> window(long timespan, TimeUnit unit, int count, Scheduler scheduler);
 Observable> window(long timespan, TimeUnit unit, Scheduler scheduler);
 Observable> window(Observable windowOpenings, Func1> closingSelector);
 Observable> window(Observable boundary);
 Observable zipWith(Iterable other, Func2 zipFunction);
 Observable zipWith(Observable other, Func2 zipFunction);
 }

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Subscribers? interface Action1 {
 void call(T t);
 }X // ...and friends! interface Func1 {
 R call(T t);
 }X
 // ...and friends! interface Observer {
 void onNext(T item);
 void onCompleted();
 void onError(Throwable t);
 }X interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }X class Observable { Observable(OnSubscribe func)
 // LOL # of methods... }

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Subscribers? interface Observer {
 void onNext(T item);
 void onCompleted();
 void onError(Throwable t);
 } interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 } class Observable { Observable(OnSubscribe func)
 // LOL # of methods... }

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Subscribers? interface Observer {
 void onNext(T item);
 void onCompleted();
 void onError(Throwable t);
 } interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }

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Subscribers? interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }X

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Subscribers? interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }X

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Subscribers? interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }X Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe();

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Subscribers? interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }X Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(new Action1() {
 @Override public void call(String item) {
 System.out.println("ITEM: " + item);
 }X
 });

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Subscribers? interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }X Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(new Observer() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }X @Override public void onError(Throwable e) { e.printStackTrace(); }X
 @Override public void onCompleted() {}
 }); 
 Action1
 call

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Subscribers? interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 }X Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe();

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Subscribers? interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 } Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s);

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Subscribers! interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 } Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s); > rx.observers.SafeSubscriber@2f2c9b19

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Subscribers! interface Subscription {
 void unsubscribe();
 boolean isUnsubscribed();
 } Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s); > rx.observers.SafeSubscriber@2f2c9b19

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/**
 * SafeSubscriber is a wrapper around Subscriber that ensures that * the Subscriber complies with the Observable contract.
 */
 class SafeSubscriber extends Subscriber {
 SafeSubscriber(Subscriber actual);
 
 Subscriber getActual();
 }

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/**
 * SafeSubscriber is a wrapper around Subscriber that ensures that * the Subscriber complies with the Observable contract.
 */
 class SafeSubscriber extends Subscriber {
 SafeSubscriber(Subscriber actual);
 
 Subscriber getActual();
 }

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/**
 * SafeSubscriber is a wrapper around Subscriber that ensures that * the Subscriber complies with the Observable contract.
 */
 class SafeSubscriber extends Subscriber {
 SafeSubscriber(Subscriber actual);
 
 Subscriber getActual();
 }

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/**
 * Provides a mechanism for receiving push-based notifications * from Observables, and permits manual unsubscribing from these * Observables.
 */
 abstract class Subscriber implements Observer, Subscription {
 Subscriber();
 Subscriber(Subscriber subscriber);
 
 void add(Subscription s);
 
 void onStart(); 
 void setProducer(Producer p);
 protected void request(long n);
 }

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/**
 * Provides a mechanism for receiving push-based notifications * from Observables, and permits manual unsubscribing from these * Observables.
 */
 abstract class Subscriber implements Observer, Subscription {
 Subscriber();
 Subscriber(Subscriber subscriber);
 
 void add(Subscription s);
 
 void onStart(); 
 void setProducer(Producer p);
 protected void request(long n);
 }

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/**
 * Provides a mechanism for receiving push-based notifications * from Observables, and permits manual unsubscribing from these * Observables.
 */
 abstract class Subscriber implements Observer, Subscription {
 Subscriber();
 Subscriber(Subscriber subscriber);
 
 void add(Subscription s);
 
 void onStart(); 
 void setProducer(Producer p);
 protected void request(long n);
 }

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Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s); > rx.observers.SafeSubscriber@2f2c9b19

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Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s); > rx.observers.SafeSubscriber@2f2c9b19 SafeSubscriber ss = (SafeSubscriber) s;

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Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s); > rx.observers.SafeSubscriber@2f2c9b19 SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());

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Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s); > rx.observers.SafeSubscriber@2f2c9b19 SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual()); > rx.Observable$26@6d311334

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Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s); > rx.observers.SafeSubscriber@2f2c9b19 SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual()); > rx.Observable$26@6d311334

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Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s); > rx.observers.SafeSubscriber@2f2c9b19 SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual()); > rx.Observable$26@6d311334

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Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s); > rx.observers.SafeSubscriber@2f2c9b19 SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual()); > rx.Observable$26@6d311334

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Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s); > rx.observers.SafeSubscriber@2f2c9b19 SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual()); > rx.Observable$26@6d311334

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public Subscription subscribe() {
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 // do nothing
 }
 
 @Override public void onCompleted() {
 // do nothing
 }
 
 @Override public void onError(Throwable e) {
 throw new OnErrorNotImplementedException(e);
 }
 });
 }

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public Subscription subscribe() {
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 // do nothing
 }
 
 @Override public void onCompleted() {
 // do nothing
 }
 
 @Override public void onError(Throwable e) {
 throw new OnErrorNotImplementedException(e);
 }
 });
 }

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public Subscription subscribe() {
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 // do nothing
 }X
 
 @Override public void onCompleted() {
 // do nothing
 }X 
 @Override public void onError(Throwable e) {
 throw new OnErrorNotImplementedException(e);
 }X
 });
 }X

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public Subscription subscribe(Action1 onNext) {
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 onNext.call(args);
 }X
 
 @Override public void onCompleted() {
 // do nothing
 }X
 
 @Override public void onError(Throwable e) {
 throw new OnErrorNotImplementedException(e);
 }X
 });
 }X 
 
 
 // do nothing

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public Subscription subscribe(Action1 onNext) {
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 onNext.call(args);
 }
 
 @Override public void onCompleted() {
 // do nothing
 }
 
 @Override public void onError(Throwable e) {
 throw new OnErrorNotImplementedException(e);
 }
 });
 }

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public Subscription subscribe(Action1 onNext) {
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 onNext.call(args);
 }
 
 @Override public void onCompleted() {
 // do nothing
 }
 
 @Override public void onError(Throwable e) {
 throw new OnErrorNotImplementedException(e);
 }
 });
 }

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public Subscription subscribe(Action1 onNext) {
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 onNext.call(args);
 }X
 
 @Override public void onCompleted() {
 // do nothing
 }X
 
 @Override public void onError(Throwable e) {
 throw new OnErrorNotImplementedException(e);
 }X
 });
 }X

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public Subscription subscribe(Observer observer) {
 if (observer instanceof Subscriber) {
 return subscribe((Subscriber) observer);
 }
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 observer.onNext(args);
 }X 
 @Override public void onCompleted() {
 observer.onCompleted();
 }X
 @Override public void onError(Throwable e) {
 observer.onError(e);
 }X
 });
 }X Action1 onNext
 
 
 onNext.call(args);
 
 
 
 // do nothing
 
 
 
 throw new OnErrorNotImplementedException(e);

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public Subscription subscribe(Observer observer) {
 if (observer instanceof Subscriber) {
 return subscribe((Subscriber) observer);
 }
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 observer.onNext(args);
 } 
 @Override public void onCompleted() {
 observer.onCompleted();
 }
 @Override public void onError(Throwable e) {
 observer.onError(e);
 }
 });
 }

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public Subscription subscribe(Observer observer) {
 if (observer instanceof Subscriber) {
 return subscribe((Subscriber) observer);
 }
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 observer.onNext(args);
 } 
 @Override public void onCompleted() {
 observer.onCompleted();
 }
 @Override public void onError(Throwable e) {
 observer.onError(e);
 }
 });
 }

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public Subscription subscribe(Observer observer) {
 if (observer instanceof Subscriber) {
 return subscribe((Subscriber) observer);
 }
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 observer.onNext(args);
 } 
 @Override public void onCompleted() {
 observer.onCompleted();
 }
 @Override public void onError(Throwable e) {
 observer.onError(e);
 }
 });
 }

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public Subscription subscribe(Observer observer) {
 if (observer instanceof Subscriber) {
 return subscribe((Subscriber) observer);
 }
 return subscribe(new Subscriber() {
 @Override public void onNext(T args) {
 observer.onNext(args);
 }X 
 @Override public void onCompleted() {
 observer.onCompleted();
 }X
 @Override public void onError(Throwable e) {
 observer.onError(e);
 }X
 });
 }X

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Observable.subscribe(Observer) Observable.subscribe(Action1) Observable.subscribe()

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Observable.subscribe() ↳ Observable.subscribe(Subscriber) Observable.subscribe(Action1) ↳ Observable.subscribe(Subscriber) Observable.subscribe(Observer) ↳ Observable.subscribe(Subscriber)

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Observable.subscribe(Action1, Action1) ↳ Observable.subscribe(Subscriber) Observable.subscribe(Action1, Action1, Action0) ↳ Observable.subscribe(Subscriber) Observable.subscribe(Observer) ↳ Observable.subscribe(Subscriber) Observable.subscribe() ↳ Observable.subscribe(Subscriber) Observable.subscribe(Action1) ↳ Observable.subscribe(Subscriber)

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Observable.subscribe(Subscriber) Observable.subscribe(Action1, Action1) ↳ Observable.subscribe(Subscriber) Observable.subscribe(Action1, Action1, Action0) ↳ Observable.subscribe(Subscriber) Observable.subscribe(Observer) ↳ Observable.subscribe(Subscriber) Observable.subscribe() ↳ Observable.subscribe(Subscriber) Observable.subscribe(Action1) ↳ Observable.subscribe(Subscriber)

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Observable.subscribe(Subscriber) ↳ ??? Observable.subscribe(Action1, Action1) ↳ Observable.subscribe(Subscriber) Observable.subscribe(Action1, Action1, Action0) ↳ Observable.subscribe(Subscriber) Observable.subscribe(Observer) ↳ Observable.subscribe(Subscriber) Observable.subscribe() ↳ Observable.subscribe(Subscriber) Observable.subscribe(Action1) ↳ Observable.subscribe(Subscriber)

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Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); System.out.println(s); > rx.observers.SafeSubscriber@2f2c9b19 SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual()); > rx.Observable$26@6d311334

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Observable o = Observable.just("Hi!");
 Subscription s = o.subscribe(); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());

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Observable o = Observable.just("Hi!");
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; Subscription s = o.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());

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Observable o = Observable.just("Hi!");
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }X
 @Override public void onError(Throwable e) {}X
 @Override public void onCompleted() {}X
 }; Subscription s = o.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());

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Observable o = Observable.just("Hi!");
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }X
 @Override public void onError(Throwable e) {}X
 @Override public void onCompleted() {}X
 }; System.out.println(in); Subscription s = o.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());

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Observable o = Observable.just("Hi!");
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); Subscription s = o.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());

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Observable o = Observable.just("Hi!");
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); Subscription s = o.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual()); > Main$1@eed1f14 > ITEM: Hi! > Main$1@eed1f14

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Observations

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Observations • The consumer of a stream is always a Subscriber.

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Observations • The consumer of a stream is always a Subscriber. • Might be wrapping an Observer, Action1, or just empty.

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Observations • The consumer of a stream is always a Subscriber. • Might be wrapping an Observer, Action1, or just empty. • Always wrapped in SafeSubscriber to ensure contract.

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Nothing

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subscribe() Subscriber Nothing

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Subscriber Nothing Action1

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Subscriber Nothing Action1 subscribe()

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Subscriber Nothing Action1 Observer

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subscribe() Subscriber Nothing Action1 Observer

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SafeSubscriber subscribe() Subscriber Nothing Action1 Observer

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SafeSubscriber Subscriber Nothing Action1 Observer

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SafeSubscriber Subscriber Nothing Action1 Observer

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Observable.subscribe(Subscriber) ↳ ??? Observable.subscribe() ↳ Observable.subscribe(Subscriber) Observable.subscribe(Action1) ↳ Observable.subscribe(Subscriber) Observable.subscribe(Action1, Action1) ↳ Observable.subscribe(Subscriber) Observable.subscribe(Action1, Action1, Action0) ↳ Observable.subscribe(Subscriber) Observable.subscribe(Observer) ↳ Observable.subscribe(Subscriber)

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Observable.subscribe(Subscriber) ↳ ???

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/**
 * Subscribes to an Observable and provides a Subscriber that * implements functions to handle the items the Observable emits * and any error or completion notification it issues.
 */
 public Subscription subscribe(Subscriber subscriber) {
 }X

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/**
 * Subscribes to an Observable and provides a Subscriber that * implements functions to handle the items the Observable emits * and any error or completion notification it issues.
 */
 public Subscription subscribe(Subscriber subscriber) {
 if (!(subscriber instanceof SafeSubscriber)) {
 subscriber = new SafeSubscriber(subscriber);
 }Y }X

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/**
 * Subscribes to an Observable and provides a Subscriber that * implements functions to handle the items the Observable emits * and any error or completion notification it issues.
 */
 public Subscription subscribe(Subscriber subscriber) {
 if (!(subscriber instanceof SafeSubscriber)) {
 subscriber = new SafeSubscriber(subscriber);
 }Y onSubscribe.call(subscriber); }X

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/**
 * Subscribes to an Observable and provides a Subscriber that * implements functions to handle the items the Observable emits * and any error or completion notification it issues.
 */
 public Subscription subscribe(Subscriber subscriber) {
 if (!(subscriber instanceof SafeSubscriber)) {
 subscriber = new SafeSubscriber(subscriber);
 }Y onSubscribe.call(subscriber); return subscriber; }X

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/**
 * Subscribes to an Observable and provides a Subscriber that * implements functions to handle the items the Observable emits * and any error or completion notification it issues.
 */
 public Subscription subscribe(Subscriber subscriber) {
 if (!(subscriber instanceof SafeSubscriber)) {
 subscriber = new SafeSubscriber(subscriber);
 }X onSubscribe.call(subscriber); return subscriber; }X class Observable { Observable(OnSubscribe func)
 // LOL # of methods... }

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/**
 * Subscribes to an Observable and provides a Subscriber that * implements functions to handle the items the Observable emits * and any error or completion notification it issues.
 */
 public Subscription subscribe(Subscriber subscriber) {
 if (!(subscriber instanceof SafeSubscriber)) {
 subscriber = new SafeSubscriber(subscriber);
 }X onSubscribe.call(subscriber); return subscriber; }X class Observable { Observable(OnSubscribe func)
 // LOL # of methods... }

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/**
 * Subscribes to an Observable and provides a Subscriber that * implements functions to handle the items the Observable emits * and any error or completion notification it issues.
 */
 public Subscription subscribe(Subscriber subscriber) {
 if (!(subscriber instanceof SafeSubscriber)) {
 subscriber = new SafeSubscriber(subscriber);
 }X onSubscribe.call(subscriber); return subscriber; }X class Observable { Observable(OnSubscribe func)
 // LOL # of methods... }

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/**
 * Subscribes to an Observable and provides a Subscriber that * implements functions to handle the items the Observable emits * and any error or completion notification it issues.
 */
 public Subscription subscribe(Subscriber subscriber) {
 if (!(subscriber instanceof SafeSubscriber)) {
 subscriber = new SafeSubscriber(subscriber);
 }X onSubscribe.call(subscriber); return subscriber; }X interface OnSubscribe extends Action1> {
 }

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/**
 * Subscribes to an Observable and provides a Subscriber that * implements functions to handle the items the Observable emits * and any error or completion notification it issues.
 */
 public Subscription subscribe(Subscriber subscriber) {
 if (!(subscriber instanceof SafeSubscriber)) {
 subscriber = new SafeSubscriber(subscriber);
 }X onSubscribe.call(subscriber); return subscriber; }X Action1>

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SafeSubscriber Subscriber Nothing Action1 Observer

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SafeSubscriber Subscriber Nothing Action1 Observer Action1>

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SafeSubscriber OnSubscribe Subscriber Nothing Action1 Observer

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Observable SafeSubscriber OnSubscribe Subscriber Nothing Action1 Observer

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Observations • The consumer of a stream is always a Subscriber. • Might be wrapping an Observer, Action1, or just empty. • Always wrapped in SafeSubscriber to ensure contract.

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Observations • The consumer of a stream is always a Subscriber. • Might be wrapping an Observer, Action1, or just empty. • Always wrapped in SafeSubscriber to ensure contract. • Observable is just a helper for passing Subscriber to OnSubscribe (aka Action1>).

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Observable greeter = Observable.just("Hi!");
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); Subscription s = greeter.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());

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Observable greeter = Observable.just("Hi!");
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); Subscription s = greeter.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());

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static Observable just(final T value) {
 }X

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static Observable just(final T value) {
 return new Observable();
 }X

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static Observable just(final T value) {
 return new Observable(new OnSubscribe() {
 @Override public void call(Subscriber s) {
 }Y
 });
 }X

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static Observable just(final T value) {
 return new Observable(new OnSubscribe() {
 @Override public void call(Subscriber s) {
 s.onNext(value);
 }Y
 });
 }X

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static Observable just(final T value) {
 return new Observable(new OnSubscribe() {
 @Override public void call(Subscriber s) {
 s.onNext(value);
 s.onCompleted();
 }Y
 });
 }X

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Observable greeter = Observable.just("Hi!");
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); Subscription s = greeter.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());

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Observable greeter = Observable.create(new OnSubscribe() {
 @Override public void call(Subscriber s) {
 s.onNext("Hi!");
 s.onCompleted();
 }
 });
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); Subscription s = greeter.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual()); just

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Observable greeter = Observable.create(new OnSubscribe() {
 @Override public void call(Subscriber s) {
 s.onNext("Hi!");
 s.onCompleted();
 }X
 });
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }Y
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); Subscription s = greeter.subscribe(in); SafeSubscriberXssX= (SafeSubscriber) s;
 System.out.println(ss.getActual()); just

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just Observable greeter = Observable.create(new OnSubscribe() {
 @Override public void call(Subscriber s) { SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());
 s.onNext("Hi!");
 s.onCompleted();
 }
 });
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }Y
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); Subscription s = greeter.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());

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Observable greeter = Observable.create(new OnSubscribe() {
 @Override public void call(Subscriber s) { SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());
 s.onNext("Hi!");
 s.onCompleted();
 }
 });
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }X
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); Subscription s = greeter.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual()); just

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Observable greeter = Observable.create(new OnSubscribe() {
 @Override public void call(Subscriber s) { SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());
 s.onNext("Hi!");
 s.onCompleted();
 }
 });
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); Subscription s = greeter.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual()); > Main$2@65ab7765 > Main$2@65ab7765 > ITEM: Hi! > Main$2@65ab7765 just

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SafeSubscriber Subscriber Nothing Action1 Observer Observable OnSubscribe

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Observable o = Observable.just("Hi!");
 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 System.out.println("ITEM: " + item);
 }X
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); Subscription s = o.subscribe(in); SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual());

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 Subscriber in = new Subscriber() {
 @Override public void onNext(String item) {
 
 }X
 @Override public void onError(Throwable e) {}
 @Override public void onCompleted() {}
 }; System.out.println(in); in SafeSubscriber ss = (SafeSubscriber) s;
 System.out.println(ss.getActual()); Observable o = Observable.just("Hi!"); Subscription s = o.subscribe(new Action1() {
 @Override public void call(String item) {
 System.out.println("ITEM: " + item);
 }X
 });Z

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Observable o = Observable.just("Hi!")
 .map(new Func1() {
 @Override public Integer call(String s) {
 return s.length();
 }
 });Y Subscription s = o.subscribe(new Action1() {
 @Override public void call(Integer item) {
 System.out.println("ITEM: " + item);
 }X
 });Z

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Observable o = Observable.just("Hi!")
 .map(new Func1() {
 @Override public Integer call(String s) {
 return s.length();
 }
 });Y Subscription s = o.subscribe(new Action1() {
 @Override public void call(Integer item) {
 System.out.println("ITEM: " + item);
 }X
 });Z

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Observable o = Observable.just("Hi!")
 .map(new Func1() {
 @Override public Integer call(String s) {
 return s.length();
 }
 });Y Subscription s = o.subscribe(new Action1() {
 @Override public void call(Integer item) {
 System.out.println("ITEM: " + item);
 }X
 });Z > ITEM: 3

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Observable o = Observable.just("Hi!")
 .map(new Func1() {
 @Override public Integer call(String s) {
 return s.length();
 }
 });Y Subscription s = o.subscribe(new Action1() {
 @Override public void call(Integer item) {
 System.out.println("ITEM: " + item);
 }X
 });Z > ITEM: 3

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Observable o = Observable.just("Hi!")
 .map(new Func1() {
 @Override public Integer call(String s) {
 return s.length();
 }
 });Y Subscription s = o.subscribe(new Action1() {
 @Override public void call(Integer item) {
 System.out.println("ITEM: " + item);
 }X
 });Z > ITEM: 3

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Observable map(Func1 func) {
 return lift(new OperatorMap(func));
 }

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Observable map(Func1 func) {
 return lift(new OperatorMap(func));
 }

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Observable map(Func1 func) {
 return lift(new OperatorMap(func));
 }

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Observable map(Func1 func) {
 return lift(new OperatorMap(func));
 }

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Observable map(Func1 func) {
 return lift(new OperatorMap(func));
 }

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Observable map(Func1 func) {
 return lift(new OperatorMap(func));
 } Observable filter(Func1 predicate) {
 return lift(new OperatorFilter(predicate));
 }

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Observable map(Func1 func) {
 return lift(new OperatorMap(func));
 } Observable filter(Func1 predicate) {
 return lift(new OperatorFilter(predicate));
 } Observable scan(R initialValue, Func2 accumulator) {
 return lift(new OperatorScan(initialValue, accumulator));
 }

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Observable map(Func1 func) {
 return lift(new OperatorMap(func));
 } Observable filter(Func1 predicate) {
 return lift(new OperatorFilter(predicate));
 } Observable scan(R initialValue, Func2 accumulator) {
 return lift(new OperatorScan(initialValue, accumulator));
 } Observable withLatestFrom(Observable other, Func2 resultSelector) {
 return lift( new OperatorWithLatestFrom(other, resultSelector));
 }

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Observable lift(Operator operator) { }

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Observable lift(Operator operator) {
 }

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Observable lift(Operator operator) {
 }X interface Operator extends Func1, Subscriber> {
 }X

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Observable lift(Operator operator) {
 }X Observable.just("Hi!")
 .map(s -> s.length()) .subscribe( new Action1 {..}); interface Operator extends Func1, Subscriber> {
 }X

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Observable lift(Operator operator) {
 }X Observable.just("Hi!")
 .map(s -> s.length()) .subscribe( new Action1 {..}); Func1 interface Operator extends Func1, Subscriber> {
 }

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Observable lift(Operator operator) {
 }X Observable.just("Hi!")
 .map(s -> s.length()) .subscribe( new Action1 {..}); Func1 Operator interface Operator extends Func1, Subscriber> {
 }X

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Observable lift(Operator operator) {
 }X Observable.just("Hi!")
 .map(s -> s.length()) .subscribe( new Action1 {..}); interface Operator extends Func1, Subscriber> {
 }X

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Observable lift(Operator operator) {
 }X Observable.just("Hi!")
 .map(s -> s.length()) .subscribe( new Action1 {..}); Subscriber interface Operator extends Func1, Subscriber> {
 }X

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Observable lift(Operator operator) {
 } Observable.just("Hi!")
 .map(s -> s.length()) .subscribe( new Action1 {..}); Subscriber interface Operator extends Func1, Subscriber> {
 } Subscriber

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Observable lift(Operator operator) {
 }X Observable.just("Hi!")
 .map(s -> s.length()) .subscribe( new Action1 {..}); Subscriber interface Operator extends Func1, Subscriber> {
 }X Operator Subscriber

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Observable lift(Operator operator) {
 }X Observable.just("Hi!")
 .map(s -> s.length()) .subscribe( new Action1 {..}); Subscriber interface Operator extends Func1, Subscriber> {
 }X Func1, Subscriber> Subscriber Operator< , >

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Observable lift(Operator operator) {
 }X

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Observable lift(Operator operator) {
 return new Observable();
 }X

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Observable lift(Operator operator) {
 return new Observable(new OnSubscribe() {
 @Override public void call(Subscriber sr) {
 }Y
 });
 }X

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Observable lift(Operator operator) {
 return new Observable(new OnSubscribe() {
 @Override public void call(Subscriber sr) {
 Subscriber st = operator.call(sr);
 }Y
 });
 }X

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Observable lift(Operator operator) {
 return new Observable(new OnSubscribe() {
 @Override public void call(Subscriber sr) {
 Subscriber st = operator.call(sr);
 onSubscribe.call(st);
 }Y
 });
 }X

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Observable map(Func1 func) {
 return lift(new OperatorMap(func));
 }

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final class OperatorMap implements Operator {
 }X

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final class OperatorMap implements Operator {
 private final Func1 func;
 
 OperatorMap(Func1 func) {
 this.func = func;
 }W
 }X

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final class OperatorMap implements Operator {
 private final Func1 func;
 
 OperatorMap(Func1 func) {
 this.func = func;
 }W
 
 @Override public Subscriber call(final Subscriber o) {
 }Y
 }X

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final class OperatorMap implements Operator {
 private final Func1 func;
 
 OperatorMap(Func1 func) {
 this.func = func;
 }W
 
 @Override public Subscriber call(final Subscriber o) {
 return new Subscriber(o) { };
 }Y
 }X

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final class OperatorMap implements Operator {
 private final Func1 func;
 
 OperatorMap(Func1 func) {
 this.func = func;
 }W
 
 @Override public Subscriber call(final Subscriber o) {
 return new Subscriber(o) {
 @Override public void onNext(T t) {
 o.onNext(func.call(t));
 }Z
 };
 }Y
 }X

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final class OperatorMap implements Operator {
 private final Func1 func;
 
 OperatorMap(Func1 func) {
 this.func = func;
 }W
 
 @Override public Subscriber call(final Subscriber o) {
 return new Subscriber(o) {
 @Override public void onNext(T t) {
 o.onNext(func.call(t));
 }Z 
 @Override public void onCompleted() { o.onCompleted(); }
 @Override public void onError(Throwable e) { o.onError(e); }
 };
 }Y
 }X

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Observations • The consumer of a stream is always a Subscriber. • Might be wrapping an Observer, Action1, or just empty. • Always wrapped in SafeSubscriber to ensure contract. • Observable is just a helper for passing Subscriber to OnSubscribe (aka Action1>).

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Observations • The consumer of a stream is always a Subscriber. • Might be wrapping an Observer, Action1, or just empty. • Always wrapped in SafeSubscriber to ensure contract. • Observable is just a helper for passing Subscriber to OnSubscribe (aka Action1>). • 
 • Operator (aka Func1,Subscriber>) changes Observable to Observable via lift().

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Observations • It's turtles Subscriber all the
 way down!

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Observable.just("Hi!")

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Observable OnSubscribe Observable.just("Hi!")

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Observable OnSubscribe Observable.just("Hi!") .map(s -> s.length())

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Observable OnSubscribe Observable.just("Hi!") .map(s -> s.length()) Func1

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Observable OnSubscribe Observable OnSubscribe Operator Observable.just("Hi!") .map(s -> s.length()) Func1

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Action1

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Action1

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Subscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 SafeSubscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 SafeSubscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 SafeSubscriber Subscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Subscriber SafeSubscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Subscriber "Hi!" SafeSubscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Subscriber "Hi!" SafeSubscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Subscriber "Hi!" SafeSubscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Subscriber 3 SafeSubscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Subscriber 3 SafeSubscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Subscriber 3 SafeSubscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Subscriber onComplete() 3 SafeSubscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Subscriber onComplete() 3 SafeSubscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 SafeSubscriber onComplete() 3 Subscriber

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 onComplete() 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation())

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) "Hi!"

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) "Hi!"

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) "Hi!"

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) "Hi!"

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation())

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation())

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) "Hi!"

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) "Hi!"

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) "Hi!"

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation())

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) Observable OnSubscribe Operator .subscribeOn(io())

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) Observable OnSubscribe Operator .subscribeOn(io())

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) Observable OnSubscribe Operator .subscribeOn(io())

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Observable OnSubscribe Observable OnSubscribe Operator Action1 Observable.just("Hi!") .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) "Hi!" Observable OnSubscribe Operator .subscribeOn(io())

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Observable OnSubscribe Observable OnSubscribe Operator Action1 httpApi.sayHi() .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) "Hi!" Observable OnSubscribe Operator .subscribeOn(io())

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Observable OnSubscribe Observable OnSubscribe Operator Action1 httpApi.sayHi() .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) "Hi!" Observable OnSubscribe Operator .subscribeOn(io())

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Observable OnSubscribe Observable OnSubscribe Operator Action1 httpApi.sayHi() .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) "Hi!" Observable OnSubscribe Operator .subscribeOn(io())

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Observable OnSubscribe Observable OnSubscribe Operator Action1 httpApi.sayHi() .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) Observable OnSubscribe Operator .subscribeOn(io()) 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 httpApi.sayHi() .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) Observable OnSubscribe Operator .subscribeOn(io()) 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 httpApi.sayHi() .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) Observable OnSubscribe Operator .subscribeOn(io()) 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 httpApi.sayHi() .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) Observable OnSubscribe Operator .subscribeOn(io()) 3

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Observable OnSubscribe Observable OnSubscribe Operator Action1 httpApi.sayHi() .map(s -> s.length()) .subscribe(..) Func1 Observable OnSubscribe Operator .observeOn(computation()) Observable OnSubscribe Operator .subscribeOn(io()) 3

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Observations • The consumer of a stream is always a Subscriber. • Observable is just a helper for passing Subscriber to OnSubscribe (aka Action1>). • Operator (aka Func1,Subscriber>) changes Observable to Observable via lift().

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Observations • The consumer of a stream is always a Subscriber. • Observable is just a helper for passing Subscriber to OnSubscribe (aka Action1>). • Operator (aka Func1,Subscriber>) changes Observable to Observable via lift(). • subscribeOn() and observeOn() are operators which change the thread a Subscriber subscribes on and is called on, respectively.

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More Resources

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More Resources • Use the source!
 https://github.com/ReactiveX/RxJava/

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More Resources • Use the source!
 https://github.com/ReactiveX/RxJava/ • "Advanced RxJava" blog series by David Karnok
 http://akarnokd.blogspot.hu/

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More Resources • Use the source!
 https://github.com/ReactiveX/RxJava/ • "Advanced RxJava" blog series by David Karnok
 http://akarnokd.blogspot.hu/ • "What if the user was a function?" by André Staltz
 https://www.youtube.com/watch?v=1zj7M1LnJV4

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RxWTF?

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RxWTF? • ReactiveX homepage
 http://reactivex.io/

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RxWTF? • ReactiveX homepage
 http://reactivex.io/ • "The introduction to Reactive Programming you've been missing"
 https://gist.github.com/staltz/868e7e9bc2a7b8c1f754

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RxWTF? • ReactiveX homepage
 http://reactivex.io/ • "The introduction to Reactive Programming you've been missing"
 https://gist.github.com/staltz/868e7e9bc2a7b8c1f754 • RxMarbles
 http://rxmarbles.com/

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RxWTF? • ReactiveX homepage
 http://reactivex.io/ • "The introduction to Reactive Programming you've been missing"
 https://gist.github.com/staltz/868e7e9bc2a7b8c1f754 • RxMarbles
 http://rxmarbles.com/ • Talks by Ben Christensen
 https://speakerdeck.com/benjchristensen

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jakewharton jakewharton jakewharton twitter.com/ google.com/+ .com Demystifying RxJava Subscribers