The Beginner's Guide to RxJava

In this talk, I'm giving some advice about how to learn RxJava.

Reference
- RxJava - Wiki
https://github.com/ReactiveX/RxJava/wiki
- RxJS
http://reactivex.io/rxjs/
- JSFiddle
https://jsfiddle.net
- RxJS Sample - hydrakecat
https://jsfiddle.net/hydrakecat/f8tv1phn/
- RxJava Operators
http://reactivex.io/documentation/operators.html
-

Transcript

1. THE BEGINNER’S GUIDE TO RXJAVA 2016.07.21
 HIROSHI KUROKAWA (@HYDRAKECAT)
2. WHAT’S RXJAVA
3. WHAT’S RXJAVA ▸ Handle a sequence of data over time as a stream ▸ Instead of gathering them, responding to each of them
4. WHAT’S RXJAVA ▸ Handle a sequence of data over time as a stream ▸ Instead of gathering them, responding to each of them 1 2 3 4 5 6
5. WHAT’S RXJAVA ▸ Handle a sequence of data over time as a stream ▸ Instead of gathering them, responding to each of them 1 2 3 4 5 6 if ( % 2 == 0) x x square( )
6. WHAT’S RXJAVA ▸ Handle a sequence of data over time as a stream ▸ Instead of gathering them, responding to each of them 1 2 3 4 5 6 if ( % 2 == 0) x x square( ) 4 16 36
7. WHAT’S RXJAVA ▸ Handle a sequence of data over time as a stream ▸ Instead of gathering them, responding to each of them Observable.just(1, 2, 3, 4, 5, 6) .filter(x -> x % 2 == 0) .map(x -> x * x) .subscribe(System.out::println);
8. WHY DIFFICULT?
9. WHY DIFFICULT? 1. Many operators
10. WHY DIFFICULT? 1. Many operators all() amb() ambWith() and() asyncAction() asyncFunc() averageDouble() averageFloat() averageInteger() averageLong() buffer() cache() cast() chunkify() collect() combineLatest() concat() concatMap() concatWith()
11. WHY DIFFICULT? 1. Many operators all() amb() ambWith() and() asyncAction() asyncFunc() averageDouble() averageFloat() averageInteger() averageLong() buffer() cache() cast() chunkify() collect() combineLatest() concat() concatMap() concatWith() connect() contains() count() countLong() create() debounce() defaultIfEmpty() defer() deferFuture() deferCancellableFuture() delay() dematerialize() distinct() distinctUntilChanged() doOnCompleted() doOnEach() doOnError() doOnNext() doOnRequest()
12. WHY DIFFICULT? 1. Many operators all() amb() ambWith() and() asyncAction() asyncFunc() averageDouble() averageFloat() averageInteger() averageLong() buffer() cache() cast() chunkify() collect() combineLatest() concat() concatMap() concatWith() connect() contains() count() countLong() create() debounce() defaultIfEmpty() defer() deferFuture() deferCancellableFuture() delay() dematerialize() distinct() distinctUntilChanged() doOnCompleted() doOnEach() doOnError() doOnNext() doOnRequest() doOnSubscribe() doOnTerminate() doOnUnsubscribe() doWhile() elementAt() elementAtOrDefault() empty() error() exists() filter() finallyDo() first() firstOrDefault() flatMap() flatMapIterable() forEach() forIterable() from() fromAction()
13. WHY DIFFICULT? 1. Many operators all() amb() ambWith() and() asyncAction() asyncFunc() averageDouble() averageFloat() averageInteger() averageLong() buffer() cache() cast() chunkify() collect() combineLatest() concat() concatMap() concatWith() connect() contains() count() countLong() create() debounce() defaultIfEmpty() defer() deferFuture() deferCancellableFuture() delay() dematerialize() distinct() distinctUntilChanged() doOnCompleted() doOnEach() doOnError() doOnNext() doOnRequest() doOnSubscribe() doOnTerminate() doOnUnsubscribe() doWhile() elementAt() elementAtOrDefault() empty() error() exists() filter() finallyDo() first() firstOrDefault() flatMap() flatMapIterable() forEach() forIterable() from() fromAction() fromCallable() fromCancellableFuture() fromFunc0() fromFuture() fromRunnable() generate() generateAbsoluteTime() getIterator() groupBy() groupByUntil() groupJoin() ifThen() ignoreElements() interval() isEmpty() join() just() last() lastOrDefault()
14. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts
15. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts ‣ Hot/Cold observable
16. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts ‣ Hot/Cold observable ‣ Scheduler
17. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts ‣ Hot/Cold observable ‣ Scheduler ‣ Subscription
18. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts ‣ Hot/Cold observable ‣ Scheduler ‣ Subscription ‣ Subject
19. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts ‣ Hot/Cold observable ‣ Scheduler ‣ Subscription ‣ Subject ‣ Back pressure
20. ADVICE 1: READ THE DOCUMENT ReactiveX/RxJava Wiki https://github.com/ReactiveX/RxJava/wiki
21. ADVISE 2: GET USED TO OPERATORS ▸ Play with Rx operators ▸ Understand how operators work with your heart
22. ADVISE 2: GET USED TO OPERATORS ▸ Play with Rx operators ▸ Understand how operators work with your heart ▸ RxJS ▸ http://reactivex.io/rxjs/ ▸ JSFiddle ▸ https://jsfiddle.net
23. SAMPLE ‣ https://jsfiddle.net/hydrakecat/f8tv1phn/
24. ADVICE 3: KNOW THE OPERATOR CATEGORIES ▸ Async ▸ Blocking Observable ▸ Combining ▸ Conditional & Boolean ▸ Connectable Observable ▸ Error Handling ▸ Filtering ▸ Mathematical and Aggregate ▸ Observable Creation ▸ String ▸ Transformational ▸ Utility Operators
25. SOME HINTS ‣ Are you interested in more than one Observables?
 → Combining / Conditional
26. SOME HINTS ‣ Are you interested in more than one Observables?
 → Combining / Conditional ‣ Or just one Observable?
 → Transforming / Filtering
27. SOME HINTS ‣ Are you interested in more than one Observables?
 → Combining / Conditional ‣ Or just one Observable?
 → Transforming / Filtering ‣ Are you creating an Observable?
 → Async / Observable Creation
28. SOME HINTS ‣ Are you interested in more than one Observables?
 → Combining / Conditional ‣ Or just one Observable?
 → Transforming / Filtering ‣ Are you creating an Observable?
 → Async / Observable Creation A Decision Tree of Observable Operators (http://reactivex.io/documentation/operators.html)
29. EXAMPLE 1: NETWORK CALL
30. EXAMPLE 1: NETWORK CALL ‣ Wait until both the network calls return and then combine the responses
31. EXAMPLE 1: NETWORK CALL ‣ Wait until both the network calls return and then combine the responses ‣ Use zipWith()
32. EXAMPLE 1: NETWORK CALL ‣ Wait until both the network calls return and then combine the responses ‣ Use zipWith() service.getDataA() .zipWith(service.getDataB(), Pair::new) .subscribeOn(Schedulers.io()) .subscribe(subscriber);
33. EXAMPLE 1: NETWORK CALL ‣ Chain a sequence of network calls
34. EXAMPLE 1: NETWORK CALL ‣ Chain a sequence of network calls ‣ Use flatMap()
35. EXAMPLE 1: NETWORK CALL ‣ Chain a sequence of network calls ‣ Use flatMap() service.getDataA() .flatMap((a) -> service.getDataB().map((b) -> new Pair<>(a, b))) .subscribeOn(Schedulers.io()) .subscribe(subscriber);
36. EXAMPLE 2: HANDLE UI EVENTS
37. EXAMPLE 2: HANDLE UI EVENTS ‣ Enable a button only when all the input fields are valid
38. EXAMPLE 2: HANDLE UI EVENTS ‣ Enable a button only when all the input fields are valid ‣ Use combineLatest()
39. EXAMPLE 2: HANDLE UI EVENTS ‣ Enable a button only when all the input fields are valid ‣ Use combineLatest() Observable.combineLatest( inputValidators, booleans -> Arrays.stream(booleans).allMatch(b -> (Boolean) b) ).subscribe(subscriber);
40. EXAMPLE 2: HANDLE UI EVENTS ‣ Pair the adjacent two events a b c d e f a, b c, d e, f b, c d, e
41. EXAMPLE 2: HANDLE UI EVENTS ‣ Pair the adjacent two events ‣ Use scan() a b c d e f a, b c, d e, f b, c d, e
42. EXAMPLE 2: HANDLE UI EVENTS ‣ Pair the adjacent two events ‣ Use scan() Observable.just("a", "b", "c", "d", "e", "f") .scan(new Pair<>(null, null), ((pair, s) -> new Pair<>(pair.second, s))) .skip(2) .subscribe(subscriber);
43. ADVICE 4: TAKE ADVANTAGE OF EXISTING RX LIBRARIES
44. ADVICE 4: TAKE ADVANTAGE OF EXISTING RX LIBRARIES ‣ Don’t create your Observable with Observable.create()
45. ADVICE 4: TAKE ADVANTAGE OF EXISTING RX LIBRARIES ‣ Don’t create your Observable with Observable.create() ‣ Use libraries instead
46. ADVICE 4: TAKE ADVANTAGE OF EXISTING RX LIBRARIES ‣ Don’t create your Observable with Observable.create() ‣ Use libraries instead ‣ Network calls: Retrofit ‣ SQLite: SQLBrite ‣ UI events: RxBinding
47. ADVICE 5: HAVE FUN! (http://slides.com/robwormald/everything-is-a-stream#/)