Reactive Frustrations

Futurice & upday

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Tomek Polanski

The Stages of Rx

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The Amazement

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0 – 4 months

The Frustration

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4 months – 1 year

Cautious Optimism

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1 year – 3+ years

Anonymous class

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button.setListener( new OnClickListener() {

@Overridepublic void onClick(View v) {

println(“Hi”); }});

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button.setListener(v -> println(“Hi”));

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Forgetting to subscribe

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just(“Will this work?”) .doOnNext(text -> println(text)) .subscribe(…)

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How Do Observables

Behave?@tpolansk

combineLatest(first, second, (f, s) -> f + s) .doOnNext(value -> println(value))

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first second

println(value) .…

concat(first, second) .doOnNext(value -> println(value))

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first second println(value)

Observable<…> getValue()Observable<…> getValueOnce()

Observable<…> getValueStream()

Observable<…> getValueOnceAndStream()

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combineLatest(firstOnce, secondOnceAndStream, (f, s) -> f + s) .doOnNext(value -> println(value))

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firstOnce secondOnceAndStream

concat(firstOnce, secondStream) .doOnNext(value -> println(value))

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firstOnce secondStream

Too Many Events

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Observable<R> x(Func1<T, Observable<R>> func)

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Func1< > func

TObservable<R> Observable<R>

flatMap, switchMap and concatMapflatMap switchMap concatMap

Crashing Errors

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getCountStream() .subscribe(count -> println(count)

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) , error -> println(error))

Costly subscribe

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create(subscriber -> subscriber.onNext(1)) .map(val -> val + 1) .filter(val -> val % 2 == 0)

create map filter

subscriber -> subscriber.onNext(1) val -> val + 1 val -> val % 2 == 0 .subscribe(val -> println(val))

just(blockingFunc())

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fromCallable(() -> blockingFunc())

just blockingFunc()

fromCallable () -> blockingFunc()

Observable<…> obs = fromCallable(() -> expensiveFunc())

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expensiveFunc()

obs.subscribe(…)obs.subscribe(…)

1x2x

Wrong Threads

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create(subscriber -> subscriber.onNext(1)) subscriber -> subscriber.onNext(1) .subscribeOn(…) .subscribeOn(…) .observeOn(…) .map(val -> val + 1)

Confusing zip

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Side-effects withdebounce

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Leaking Subscriptions

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Subscription s = getCountStream() .subscribe(…)

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subscribeSubscription s

…

s

s.unsubscribe()

Logging Wrong Events

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getCountStream()

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.doOnNext(count -> println(count)) .doOnNext(count -> println(count)) .doOnEach(notify -> println(notify))

The Conclusion

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No More Thread Synchronization

+Transforming Async Events

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Can Make Application Truly Reactive

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Rx Is Just a Tool

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Don’t Be Dogmatic

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Questions, Feedback &

Frustrations@tpolansk