Applying Rx Best Practices to Your Architecture

Video: https://youtu.be/ohBumH5-3Qs

Your relationship with RxJava doesn't have to be complicated. We find many ways to use it wrong; it is also powerful when used properly. In fact, RxJava can guide you in shaping a sound architecture for your app. We only have to follow a few but decisive principles.

In this talk, we'll:

- See at how side-effect isolation can help avoiding bugs.
- Learn how to share one unique stream between your view and your presenter.
- Discover the ways a unidirectional data flow makes adding new functionality easy and safe.
- Look at how data immutability brings safety to data manipulation.

After this talk, you’ll be able to write a robust and reactive architecture for your app, taking full advantage of RxJava.

Transcript

1. Benoît Quenaudon @oldergod Applying Rx Best Practices to your Architecture
2. Side-Effects Isolation
3. class ProfileView {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() fun onStart() {k }i }z
4. class ProfileView {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() fun onStart() {k nameSubject@ .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) }i }z
5. class ProfileView {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() fun onStart() {k nameSubject@ .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) }i }z
6. class ProfileView {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() fun onStart() {k nameSubject@ .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) // hint grows the view in width so hide it if unnecessary nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) }i }z
7. class ProfileView {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() fun onStart() {k nameSubject@ .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) // hint grows the view in width so hide it if unnecessary nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) appService.profile().subscribe(this::populateProfile) }i }z
8. class ProfileView {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() fun onStart() {k nameSubject .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) // hint grows the view in width so hide it if unnecessary nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) appService.profile().subscribe(this::populateProfile) }i fun populateProfile(profile: Profile) {h nameSubject.onNext(profile.name) // rendering other stuff }g }z
9. class ProfileView {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() fun onStart() {k nameSubject .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) // hint grows the view in width so hide it if unnecessary nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) appService.profile().subscribe(this::populateProfile) }i fun populateProfile(profile: Profile) {h nameSubject.onNext(profile.name) // rendering other stuff }g fun onSetNameDialogResult(newName: String) = setName(newName) }z
10. val appService: AppService val nameSubject = BehaviorSubject.create<String>() fun onStart() {k nameSubject .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) // hint grows the view in width so hide it if unnecessary nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) appService.profile().subscribe(this::populateProfile) }i fun populateProfile(profile: Profile) {h nameSubject.onNext(profile.name) // rendering other stuff }g fun onSetNameDialogResult(newName: String) = setName(newName) fun setName(newName: String) {f nameSubject.onNext(newName) }b }z
11. fun onStart() {k nameSubject .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) // hint grows the view in width so hide it if unnecessary nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) appService.profile().subscribe(this::populateProfile) }i fun populateProfile(profile: Profile) {h nameSubject.onNext(profile.name) // rendering other stuff }g fun onSetNameDialogResult(newName: String) = setName(newName) fun setName(newName: String) {f nameSubject.onNext(newName) appService.setName(newName) .subscribe { response -> when {e response.isValid -> nameSubject.onNext(response.name) response.isInvalid -> navigator.goTo(response.error) }d }c }b
12. fun onStart() {k nameSubject .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) // hint grows the view in width so hide it if unnecessary nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) appService.profile().subscribe(this::populateProfile) }i fun populateProfile(profile: Profile) {h nameSubject.onNext(profile.name) // rendering other stuff }g fun onSetNameDialogResult(newName: String) = setName(newName) fun setName(newName: String) {f nameSubject.onNext(newName) appService.setName(newName) .subscribe { response -> when {e response.isValid -> nameSubject.onNext(response.name) response.isInvalid -> navigator.goTo(response.error) }d }c }b
13. fun onStart() {k nameSubject .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) // hint grows the view in width so hide it if unnecessary nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) appService.profile().subscribe(this::populateProfile) }i fun populateProfile(profile: Profile) {h nameSubject.onNext(profile.name) // rendering other stuff }g fun onSetNameDialogResult(newName: String) = setName(newName) fun setName(newName: String) {f nameSubject.onNext(newName) appService.setName(newName) .subscribe { response -> when {e response.isValid -> nameSubject.onNext(response.name) response.isInvalid -> navigator.goTo(response.error) }d }c }b
14. fun onStart() {k nameSubject .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) // hint grows the view in width so hide it if unnecessary nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) appService.profile().subscribe(this::populateProfile) }i fun populateProfile(profile: Profile) {h nameSubject.onNext(profile.name) // rendering other stuff }g fun onSetNameDialogResult(newName: String) = setName(newName) fun setName(newName: String) {f nameSubject.onNext(newName) appService.setName(newName) .subscribe { response -> when {e response.isValid -> nameSubject.onNext(response.name) response.isInvalid -> navigator.goTo(response.error) }d }c }b
15. How about Side Effects?
16. fun onStart() {k nameSubject .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) // hint grows the view in width so hide it if unnecessary nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) appService.profile().subscribe(this::populateProfile) }i fun populateProfile(profile: Profile) {h nameSubject.onNext(profile.name) // rendering other stuff }g fun onSetNameDialogResult(newName: String) = setName(newName) fun setName(newName: String) {f nameSubject.onNext(newName) appService.setName(newName) .subscribe { response -> when {e response.isValid -> nameSubject.onNext(response.name) response.isInvalid -> navigator.goTo(response.error) }d }c }b
17. fun onStart() {k nameSubject .switchMap { name -> appService.profile() .map { profile -> profile.prefix } .map { profile -> if (name.isEmpty()) "" else "$prefix $name" } }j .subscribe(nameView::setText) // hint grows the view in width so hide it if unnecessary nameSubject .map { name -> if (name.isEmpty()) "Set your name" else "" } .subscribe(nameView::setHint) appService.profile().subscribe(this::populateProfile) }i fun populateProfile(profile: Profile) {h nameSubject.onNext(profile.name) // rendering other stuff }g fun onSetNameDialogResult(newName: String) = setName(newName) fun setName(newName: String) {f nameSubject.onNext(newName) appService.setName(newName) .subscribe { response -> when {e response.isValid -> nameSubject.onNext(response.name) response.isInvalid -> navigator.goTo(response.error) }d }c }b
18. class ProfileViewRemix {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() fun onStart() {t }i }t
19. sealed class Event { data class EditName(val newName: String) : Event() }
20. sealed class Result { data class ProfileResult(val profile: Profile) : Result() data class NameValid(val name: String) : Result() object NameInvalid : Result() }
21. data class ViewModel( val stuff: Any?, val prefixedName: PrefixedName )a
22. data class ViewModel( val stuff: Any?, val prefixedName: PrefixedName )a{ data class PrefixedName( val prefix: String, val name: String ) { fun compute(name:String): String = if (name.isEmpty()) "" else "$prefix $name" } }
23. class ProfileViewRemix {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() fun onStart() {t }i }t
24. class ProfileViewRemix {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() val events = PublishSubject.create<Event>() fun onStart() {t events.flatMap { event -> }i }t
25. class ProfileViewRemix {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() val events = PublishSubject.create<Event>() fun onStart() {t events.flatMap { event -> .subscribe { viewModel -> }o }i }t
26. class ProfileViewRemix {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() val events = PublishSubject.create<Event>() fun onStart() {t events.flatMap { event -> .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i }t
27. class ProfileViewRemix {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() val events = PublishSubject.create<Event>() fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> }g }h .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i }t
28. class ProfileViewRemix {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() val events = PublishSubject.create<Event>() fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f }g }h .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i }t
29. class ProfileViewRemix {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() val events = PublishSubject.create<Event>() fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i }t
30. class ProfileViewRemix {a val navigator: Navigator val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() val events = PublishSubject.create<Event>() fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i }t
31. val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() val events = PublishSubject.create<Event>() fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i }t
32. val nameView: TextView val appService: AppService val nameSubject = BehaviorSubject.create<String>() val events = PublishSubject.create<Event>() fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i }t
33. val events = PublishSubject.create<Event>() fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous }l })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i }t
34. fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )k }l })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o
35. fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )k }l })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i fun onSetNameDialogResult(newName: String) {u events.onNext(EditName(newName)) }y }t
36. fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )k }l })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i fun onSetNameDialogResult(newName: String) {u events.onNext(EditName(newName)) }y }t
37. fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )k }l })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i fun onSetNameDialogResult(newName: String) {u events.onNext(EditName(newName)) }y
38. fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )k }l })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i fun onSetNameDialogResult(newName: String) {u events.onNext(EditName(newName)) }y
39. fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )k }l })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i fun onSetNameDialogResult(newName: String) {u events.onNext(EditName(newName)) }y
40. fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )k }l })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i fun onSetNameDialogResult(newName: String) {u events.onNext(EditName(newName)) }y
41. One Stream Many Options
42. fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )k }l })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i fun onSetNameDialogResult(newName: String) {u events.onNext(EditName(newName)) }y
43. fun onStart() {t events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) } }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )k }l })p .subscribe { viewModel -> nameView.hint = if (viewModel.prefixedName.name.isEmpty()) "Set your name" else "" nameView.text = viewModel.prefixedName.compute() // rendering other stuff }o }i fun onSetNameDialogResult(newName: String) {u events.onNext(EditName(newName)) }y
44. events // Observable<Event> .subscribe { viewModel -> }o
45. events // Observable<Event> <!-- prezenter --> .subscribe { viewModel -> }o
46. Passing events to the Presenter
47. Option A Passing events to the Presenter
48. events .subscribe { viewModel -> }o class ProfilePresenter : Consumer<Event> { }z View Presenter
49. events .subscribe { viewModel -> }o class ProfilePresenter : Consumer<Event> { override fun accept(event: Event) { }a }z View Presenter
50. events .subscribe(presenter) .subscribe { viewModel -> }o class ProfilePresenter : Consumer<Event> { override fun accept(event: Event) { }a }z View Presenter
51. events .subscribe(presenter) .subscribe { viewModel -> }o class ProfilePresenter : Consumer<Event> { override fun accept(event: Event) { event.flatMap {} }a }z View Presenter
52. Observable.just(1, 2, 3) .subscribe { int -> Observable.just(int * 3) .subscribe { println(it) } }
53. Option B Passing events to the Presenter
54. events. .subscribe { viewModel -> }o class ProfilePresenter(val events:Observable<Event>) { }z View Presenter
55. events. .subscribe { viewModel -> }o class ProfilePresenter(val events:Observable<Event>) { init { events.flatMap { event -> } }a }z View Presenter
56. presenter(events) .subscribe { viewModel -> }o class ProfilePresenter(val events:Observable<Event>) { init { events.flatMap { event -> } }a }z View Presenter
57. Option C Passing events to the Presenter
58. presenter.somefunction(events) .subscribe { viewModel -> }o class ProfilePresenter { fun somefunction(events: Observable<Event>) { events.flatMap { event -> } } } View Presenter
59. Passing view models to the View
60. Option A Passing view models to the View
61. presenter.viewmodels() .subscribe { viewModel -> }o class ProfilePresenter { fun viewmodels(): Observable<ViewModel> { } } View Presenter
62. Option B Passing view models to the View
63. presenter .subscribe { viewModel -> }o class ProfilePresenter: Observable<ViewModel>() { override fun subscribeActual(observer: Observer<in ViewModel>) { } } View Presenter
64. Option C Passing view models to the View
65. presenter .subscribe() class ProfilePresenter: ObservableSource<ViewModel> { override fun subscribe(observer: Observer<in ViewModel>) { }a }z View Presenter
66. presenter .subscribe(object : Observer<ViewModel> { override fun onComplete() {} override fun onSubscribe(d: Disposable) {} override fun onNext(t: ViewModel) {} override fun onError(e: Throwable) {} }) class ProfilePresenter: ObservableSource<ViewModel> { override fun subscribe(observer: Observer<in ViewModel>) { }a }z View Presenter
67. Observable.wrap(presenter) .subscribe { viewModel -> }o class ProfilePresenter: ObservableSource<ViewModel> { override fun subscribe(observer: Observer<in ViewModel>) { }a }z View Presenter
68. Writing is good. Thinking is better.
69. fun presenter():
70. fun presenter(events: Observable<Event>):
71. fun presenter(events: Observable<Event>): Observable<ViewModel>
72. interface ObservableTransformer<Upstream, Downstream> {a /** * Applies a function to the upstream Observable and returns an ObservableSource with * optionally different element type. */ fun apply(upstream: Observable<Upstream>): ObservableSource<Downstream> }b
73. interface ObservableTransformer<Upstream, Downstream> {a fun apply(upstream: Observable<Upstream>): ObservableSource<Downstream> }b
74. interface ObservableTransformer<Event, Downstream> {a fun apply(events: Observable<Event>): ObservableSource<Downstream> }b
75. interface ObservableTransformer<Event, ViewModel> {a fun apply(events: Observable<Event>): ObservableSource<ViewModel> }b
76. class Presenter: ObservableTransformer<Event, ViewModel> {a fun apply(events: Observable<Event>): ObservableSource<ViewModel> }b
77. class Presenter: ObservableTransformer<Event, ViewModel> {a fun apply(events: Observable<Event>): ObservableSource<ViewModel> }b events .compose(presenter) .subscribe { viewModel -> }o View Presenter
78. class Presenter: ObservableTransformer<Event, ViewModel> {a fun apply(events: Observable<Event>): ObservableSource<ViewModel> }b val testObserver = events // PublishSubject<Event> .compose(presenter) .test() // TestObserver<ViewModel> Test Presenter
79. class Presenter: ObservableTransformer<Event, ViewModel> {a fun apply(events: Observable<Event>): ObservableSource<ViewModel> }b val testObserver = events // PublishSubject<Event> .compose(presenter) .test() // TestObserver<ViewModel> events.onNext(EditName("Georges")) testObserver.assertValue(ViewModel()) Test Presenter
80. Thinking is good. Config Changes is better.
81. presenter.viewModels() .subscribe { viewModel -> }o class ProfilePresenter {j }u View Presenter
82. presenter.viewModels() .subscribe { viewModel -> }o class ProfilePresenter {j val events = PublishSubject.create<Event>() fun passEvents(events: Observable<Event>) {k events.subscribe(this.events) }l }u View Presenter
83. presenter.viewModels() .subscribe { viewModel -> }o class ProfilePresenter {j val events = PublishSubject.create<Event>() fun passEvents(events: Observable<Event>) {k events.subscribe(this.events) }l fun viewModels() {o return events
 .businessLogic() }i }u View Presenter
84. presenter.viewModels() .subscribe { viewModel -> }o class ProfilePresenter {j val events = PublishSubject.create<Event>() fun passEvents(events: Observable<Event>) {k events.subscribe(this.events) }l fun viewModels() {o return events
 .businessLogic()
 .replay(1)
 .autoConnect(0) }i }u View Presenter
85. presenter.viewModels() .subscribe { viewModel -> }o class ProfilePresenter {j val events = PublishSubject.create<Event>() fun passEvents(events: Observable<Event>) {k events.subscribe(this.events) }l fun viewModels() {o return events
 .businessLogic()
 .replay(1)
 .autoConnect(0) }i }u View Presenter
86. presenter.viewModels() .subscribe { viewModel -> }o
 presenter.passEvents(events) class ProfilePresenter {j val events = PublishSubject.create<Event>() fun passEvents(events: Observable<Event>) {k events.subscribe(this.events) }l fun viewModels() {o return events
 .businessLogic()
 .replay(1)
 .autoConnect(0) }i }u View Presenter
87. Unidirectional Data Flow
88. VIEW PRESENTER
89. VIEW PRESENTER (BUSINESS LOGIC) READING WRITING
90. VIEW PRESENTER (BUSINESS LOGIC) VIEW (READING) VIEW (WRITING)
91. VIEW (READING) VIEW (WRITING) PRESENTER (BUSINESS LOGIC)
92. VIEW (READING) VIEW (WRITING) PRESENTER (BUSINESS LOGIC)
93. New Feature? No Problem.
94. sealed class Event { data class EditName(val newName: String) : Event() }a data class ViewModel( val stuff: Any?, val prefixedName: PrefixedName )b class ProfileViewRemix { fun onStart() {t events .compose(presenter) .subscribe { viewModel -> // rendering view model }o }i }t
95. sealed class Event { data class EditName(val newName: String) : Event() }a data class ViewModel( val stuff: Any?, val prefixedName: PrefixedName )b class ProfileViewRemix { fun onStart() {t events .compose(presenter) .subscribe { viewModel -> // rendering view model }o }i }t
96. sealed class Event { data class EditName(val newName: String) : Event() data class ChangeAvatar(val picture: File) : Event() }a data class ViewModel( val stuff: Any?, val prefixedName: PrefixedName )b class ProfileViewRemix { fun onStart() {t events .compose(presenter) .subscribe { viewModel -> // rendering view model }o }i }t
97. sealed class Event { data class EditName(val newName: String) : Event() data class ChangeAvatar(val picture: File) : Event() }a data class ViewModel( val stuff: Any?, val prefixedName: PrefixedName, val avatarUri: Uri )b class ProfileViewRemix { fun onStart() {t events .compose(presenter) .subscribe { viewModel -> // rendering view model }o }i }t
98. sealed class Event { data class EditName(val newName: String) : Event() data class ChangeAvatar(val picture: File) : Event() }a data class ViewModel( val stuff: Any?, val prefixedName: PrefixedName, val avatarUri: Uri )b class ProfileViewRemix { fun onStart() {t events .compose(presenter) .subscribe { viewModel -> // rendering view model Picasso.get().load(viewModel.avatarUri).into(avatarView) }o }i }t
99. class ProfilePresenter : ObservableTransformer<Event, ViewModel> {a override fun apply(events: Observable<Event>): ObservableSource<ViewModel> {d return events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) }s }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )f }g })h }j }k
100. class ProfilePresenter : ObservableTransformer<Event, ViewModel> {a override fun apply(events: Observable<Event>): ObservableSource<ViewModel> {d return events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) }s }d }f .startWith(NameValid(event.newName)) }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )f }g })h }j }k
101. class ProfilePresenter : ObservableTransformer<Event, ViewModel> {a override fun apply(events: Observable<Event>): ObservableSource<ViewModel> {d return events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) }s }d }f .startWith(NameValid(event.newName)) is ChangeAvatar -> appService.changeAvatar(event.picture) .map { response -> AvatarValid(response.uri) } }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )f }g })h }j }k
102. class ProfilePresenter : ObservableTransformer<Event, ViewModel> {a override fun apply(events: Observable<Event>): ObservableSource<ViewModel> {d return events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) }s }d }f .startWith(NameValid(event.newName)) is ChangeAvatar -> appService.changeAvatar(event.picture) .map { response -> AvatarValid(response.uri) } .onErrorReturn { throwable -> AvatarInvalid(throwable) } }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )f }g })h }j }k
103. class ProfilePresenter : ObservableTransformer<Event, ViewModel> {a override fun apply(events: Observable<Event>): ObservableSource<ViewModel> {d return events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) }s }d }f .startWith(NameValid(event.newName)) is ChangeAvatar -> appService.changeAvatar(event.picture) .map { response -> AvatarValid(response.uri) } .onErrorReturn { throwable -> AvatarInvalid(throwable) } }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )f is AvatarValid -> previous.copy(avatarUri = result.uri) }g })h }j
104. override fun apply(events: Observable<Event>): ObservableSource<ViewModel> {d return events.flatMap { event -> when (event) {y is EditName -> appService.setName(event.newName) .map { response -> when {u response.isValid -> NameValid(response.name) response.isInvalid -> NameInvalid.also { navigator.goTo(response) }s }d }f .startWith(NameValid(event.newName)) is ChangeAvatar -> appService.changeAvatar(event.picture) .map { response -> AvatarValid(response.uri) } .onErrorReturn { throwable -> AvatarInvalid(throwable) } }g }h .mergeWith(appService.profile().map(::ProfileResult)) .scan(ViewModel(stuff = null, prefixedName = PrefixedName("", "")), BiFunction { previous: ViewModel, result: Result -> when (result) {j is NameValid -> previous.copy(prefixedName = previous.prefixedName.copy(name = result.name)) is NameInvalid -> previous is ProfileResult -> previous.copy( stuff = result.profile, prefixedName = PrefixedName(result.profile.prefix, result.profile.name) )f is AvatarValid -> previous.copy(avatarUri = result.uri) is AvatarInvalid -> TODO() }g })h }j
105. Architecture forced us to separate concerns No need to touch existing code Easy to test Easy to review
106. Gotta Immutate 'em All! Unidirectional Data Flow Side-Effects Isolation
107. Benoît Quenaudon @oldergod Fin