MVP & RxJava

Collaborative talk with Niklas Baudy (https://twitter.com/vanniktech)

We'll talk about the upcoming release of RxJava 2 and how to use MVP in a reactive manner.
What we'll talk about:
- RxJava 1 (History, basic introduction)
- RxJava 2 (Reason / Motivation, What's new / What stayed)
- MVP with RxJava 2 + RxBinding

Transcript

1. MVP & RxJava
2. What is Rx? • Reactive Functional Programming • Push instead of pull principle • Marble diagrams
3. RxJava 1.x
4. RxJava 1.x - Observable
5. RxJava 1.x - Single • Single<T> since version 1.0.13 (July, 2015) • @Beta
6. RxJava 1.x - Completable • Completable since version 1.1.1 (February, 2016) • @Experimental
7. RxJava 1.x - Operators
8. RxJava 1.x - Operators
9. RxJava 1.x - Operators
10. RxJava 1.x - Operators
11. RxJava 1.x - Operators
12. RxJava 1.x - Observable / Single subscribe • Subscription subscribe(Observer<T>) • Lambdas support too • Safe Subscribe
13. RxJava 1.x - Backpressure
14. RxJava 1.x - Backpressure • Observable “mostly” supports it ◦ onBackPressureXXX() • Single & Completable do not support Backpressure
15. RxJava 2.0
16. RxJava 2.0 - Timeline • Still under development • 2.0.0-RC1 (25th August 2016) • 2.0.0-RC2 (5th September 2016) • 2.0.0-RC3 (23rd September 2016) • 2.0.0-RC4 (7th October 2016) • 2.0.0-RC5 (21st October 2016) • 2.0.0 (28th October 2016)
17. RxJava 2.0 - Reasons • Reactive Streams Specification • New breaking API • Avoid / smoothen out some mistakes • Less allocations / overhead
18. RxJava 2.0 - What changed? • Different package name • Different Artifact Id • null is forbidden • New Reactive Base Types (Flowable & Maybe) • Subscription management • Better conversion and integration between Reactive Base Types
19. RxJava 2.0 - null is forbidden • Basically no nulls are allowed • Observable.just(null) • Observable.just(1, null) • Single.just(null) • Single.error(null) • Single.fromCallable(() -> null)
20. RxJava 2.0 - Reactive Base Types • Observable<T> • Single<T> • Completable • Flowable<T> • Maybe<T>
21. RxJava 2.0 - Flowable
22. RxJava 2.0 - Backpressure
23. RxJava 2.0 - Maybe
24. RxJava 2.0 - Subscribing • Observable: void subscribe(Observer<T>) • Flowable: void subscribe(Subscriber<T>) • subscribeWith() • No safe subscribe • Lambdas support too
25. RxJava 2.0 - Better Integration • Single<T> first(default) • Maybe<T> firstElement() • Single<T> firstOrError() • Maybe<T> last() • Maybe<T> elementAt(index)
26. RxJava 2.0 - Tricks: test()
27. RxJava 2.0 - Tricks: Scheduling
28. RxJava 2.0 - Tricks: flatMap*
29. RxJava 2.0 - Early Adopters • RxAndroid • https://github.com/ReactiveX/RxAndroid • Retrofit Adapter • https://github.com/JakeWharton/retrofit2-rxjava2-adapter
30. RxJava 2.0 <-> RxJava 1.x • Adapter by the Lead RxJava Developer (David) • https://github.com/akarnokd/RxJava2Interop
31. MVP
32. MVP::motivation • Android Platform Types are untestable • Separation of UI & Business Logic • Forces structure and layering
33. MVP::in a nutshell • Presenter - contains the business logic ◦ Acts upon the Model & the View ◦ Responsible for retrieving data (the Model) ◦ Responsible for formatting the data for display (in the View) • View - interface/contract that displays data ◦ ≠ android.view.View ◦ Routes user events to the Presenter ◦ Usually implemented by Activity, Fragment or ViewGroup • Model - defines the data that needs to be displayed
34. MVP::in a nutshell View Presenter Model
35. Imperative MVP
36. Imperative MVP
37. Imperative MVP
38. Small detour… ↷
39. RxBinding • RxJava apis for Android UI widgets • Bindings for platform views, as well as for support library views • Provides Kotlin extension functions • No RxJava 2.0 adaptation at the moment • Not safe with RxJava2Interop
40. RxBinding::motivation • View events == Stream of Data • Seamless integration into Reactive sequences • Observable creation requires a great deal of ceremony ◦ Especially without leaking the view
41. RxBinding::without
42. RxBinding::with
43. RxBinding::more examples
44. RxBinding::more examples
45. Reactive MVP • Same principle as Imperative MVP • With two major differences: ◦ The view propagates UI events as Reactive Streams ◦ The presenter exposes only one method which returns a Disposable
46. Reactive MVP
47. Reactive MVP
48. Reactive MVP
49. Reactive MVP::takeaways • User input may also create Backpressure ◦ Consider Flowable or Observable#filter()/Observable#debounce() • Keep your presenters simple • A ‘View’ is not always an actual UI representation https://github.com/serj-lotutovici/RxMVP
50. Thank you! @vanniktech vanniktech serj-lotutovici @SerjLtt Observable.just(❓) .map(❓ -> ) .subscribe( );