Slides about Viper on Android presented on the Android Dev Conference 2017. https://eventos.imasters.com.br/android-devconference

1. VIPER ON ANDROID
Gabriel B. Zandavalle
Thiago “Fred” Porciúncula

2. • Clean Architecture
• What is VIPER
• Cases
• Code samples
• Cons e Pros
• Architecture Components
• Questions

3. CLEAN ARCHITECTURE | WHAT IT IS?
https://8thlight.com/blog/uncle-bob/2012/08/13/the-clean-architecture.html

4. CLEAN ARCHITECTURE | WHAT IT IS?

7. VIPER

8. CLEAN ARCHITECTURE | VIPER
VIPER IS AN APPLICATION OF CLEAN ARCHITECTURE
TO IOS APPS (AND NOW ANDROID!)

9. V - View
I - Interactor
P - Presenter
E - Entity
R - Routing
VIPER | WHAT DOES IT MEAN?

10. VIEW
Displays what it is told to by the Presenter and relays
user input back to the Presenter.

11. PRESENTER
Contains view logic for preparing content for display (as
received from the Interactor) and for reacting to user
inputs (by requesting new data from the Interactor).

12. INTERACTOR
Contains the business logic as specified by a use case.

13. ENTITY
Contains basic model objects used by the Interactor.

14. ROUTING
Contains navigation logic for describing which
screens are shown in which order.

15. VIPER | MODULE

16. WHY VIPER ON ANDROID?

17. CASES | UBER
https://eng.uber.com/new-rider-app/

18. CASES | UBER

19. CASES | BRAGI
http://luboganev.github.io/blog/clean-architecture-pt1/

20. CASES | COURSERA
https://news.realm.io/news/360andev-richa-khandelwal-effective-
android-architecture-patterns-java/

21. CASES | COURSERA

22. CASES | COURSERA

23. CASES | COURSERA

24. View Presenter Interactor
Router
Dagger
Entity

25. VIPER | MODULE
HomeActivity
HomePresenterOutput
HomePresenter HomeInteractor
HomePresenterInput
HomeInteractorOutput
HomeInteractorInput

26. class HomeContracts {
interface HomePresenterInput {
fun viewLoaded()
}
interface HomeInteractorInput {
fun loadMovies()
}
interface HomeInteractorOutput {
fun moviesLoaded(items: List<Movie>)
}
interface HomePresenterOutput {
fun showMovies(items: List<Movie>)
}
}
VIPER | CONTRACTS

27. class HomeContracts {
interface HomePresenterInput {
fun viewLoaded()
}
interface HomeInteractorInput {
fun loadMovies()
}
interface HomeInteractorOutput {
fun moviesLoaded(items: List<Movie>)
}
interface HomePresenterOutput {
fun showMovies(items: List<Movie>)
}
}
VIPER | CONTRACTS
HomeActivity
HomePresenterOutpu
HomePresenter HomeInteractor
HomePresenterInput
HomeInteractorOutpu
HomeInteractorInput

28. class HomeActivity: AppCompatActivity(), HomeContracts.HomePresenterOutput {
@Inject
lateinit var homePresenterInput: HomeContracts.HomePresenterInput
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_home)
injectDependencies()
homePresenterInput.viewLoaded()
}
override fun showMovies(items: List<Movie>) {
moviesRecyclerView.adapter = MovieAdapter(items)
moviesRecyclerView.layoutManager = LinearLayoutManager(this)
}
}
VIPER | VIEW

29. class HomeActivity: AppCompatActivity(), HomeContracts.HomePresenterOutput {
@Inject
lateinit var homePresenterInput: HomeContracts.HomePresenterInput
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_home)
injectDependencies()
homePresenterInput.viewLoaded()
}
override fun showMovies(items: List<Movie>) {
moviesRecyclerView.adapter = MovieAdapter(items)
moviesRecyclerView.layoutManager = LinearLayoutManager(this)
}
}
VIPER | VIEW
HomeActivity
HomePresenterOutpu
HomePresenter HomeInteractor
HomePresenterInput
HomeInteractorOutpu
HomeInteractorInput
viewLoaded()
showMovies()

30. VIPER | PRESENTER
class HomePresenter(
private val homePresenterOutput: HomePresenterOutput,
private val homeInteractorInput: HomeInteractorInput) :
HomePresenterInput, HomeInteractorOutput {
override fun viewLoaded() {
homeInteractorInput.loadMovies()
}
override fun moviesLoaded(items: List<Movie>) {
homePresenterOutput.showMovies(items)
}
}

31. VIPER | PRESENTER
class HomePresenter(
private val homePresenterOutput: HomePresenterOutput,
private val homeInteractorInput: HomeInteractorInput) :
HomePresenterInput, HomeInteractorOutput {
override fun viewLoaded() {
homeInteractorInput.loadMovies()
}
override fun moviesLoaded(items: List<Movie>) {
homePresenterOutput.showMovies(items)
}
}
HomeActivity
HomePresenterOutpu
HomePresenter HomeInteractor
HomePresenterInput
HomeInteractorOutpu
HomeInteractorInput
viewLoaded() loadMovies()
moviesLoaded()showMovies()

32. VIPER | INTERACTOR
class HomeInteractor(private val moviesApi: MoviesAPI) : HomeInteractorInput {
lateinit var homeInteractorOutput: HomeInteractorOutput
override fun loadMovies() {
moviesApi.getList("1", "api_key").subscribe ({
homeInteractorOutput.moviesLoaded(it.items)
}, {
Log.e(TAG, "Error loading movies", it)
})
}
}

33. VIPER | INTERACTOR
class HomeInteractor(private val moviesApi: MoviesAPI) : HomeInteractorInput {
lateinit var homeInteractorOutput: HomeInteractorOutput
override fun loadMovies() {
moviesApi.getList("1", "api_key").subscribe ({
homeInteractorOutput.moviesLoaded(it.items)
}, {
Log.e(TAG, "Error loading movies", it)
})
}
}
HomeActivity
HomePresenterOutpu
HomePresenter HomeInteractor
HomePresenterInput
HomeInteractorOutpu
HomeInteractorInput
loadMovies()
moviesLoaded()

34. VIPER | ENTITY
data class Movie(
val id: String = "",
val posterPath: String = "",
val title: String = "",
val overview: String = "",
val releaseDate : String = ""
)
}

35. VIPER | ROUTER
class HomeRouter(private val context: Context) {
fun navigateToDetail(id: String) {
val intent = Intent(context, DetailActivity::class.java)
intent.putExtra(
DetailActivity.EXTRA_SELECTED_MOVIE_ID, id)
context.startActivity(intent)
}
}

36. VIPER | TESTS
@Mock
lateinit var homePresenterOutput: HomeContracts.HomePresenterOutput
@Mock
lateinit var homeInteractorInput: HomeContracts.HomeInteractorInput
@Before
fun setUp() {
MockitoAnnotations.initMocks(this)
homePresenter = HomePresenter(homePresenterOutput, homeInteractorInput)
homePresenter.setPresenterOutput(homePresenterOutput)
given(homeInteractorInput.loadMovies()).will { homePresenter.moviesLoaded(movies) }
}

37. VIPER | TESTS
@Test
fun shouldLoadMoviesWhenViewIsLoaded() {
homePresenter.viewLoaded()
verify(homeInteractorInput).loadMovies()
}
@Test
fun shouldShowMoviesWhenMoviesAreLoaded() {
homePresenter.moviesLoaded(movies)
verify(homePresenterOutput).showMovies(movies)
}

38. VIPER | MODULES

39. VIPER | CONS

40. VIPER | CONS
• Overkill for small projects

41. VIPER | CONS
• Overkill for small projects
• Overhead for inexperienced teams and risk of
mixing it with different strategies (MVP/MVC/
MVVM)

42. VIPER | CONS
• Overkill for small projects
• Overhead for inexperienced teams and risk of
mixing it with different strategies (MVP/MVC/
MVVM)
• Tedious modules creation without code generators

43. VIPER | CONS
• Overkill for small projects
• Overhead for inexperienced teams and risk of
mixing it with different strategies (MVP/MVC/
MVVM)
• Tedious modules creation without code generators
• Might not be a perfect fit for any kind of project

44. VIPER | PROS

45. VIPER | PROS
• Improved responsibility balance

46. VIPER | PROS
• Improved responsibility balance
• Well-defined contracts

47. VIPER | PROS
• Improved responsibility balance
• Well-defined contracts
• Smaller classes and methods

48. VIPER | PROS
• Improved responsibility balance
• Well-defined contracts
• Smaller classes and methods
• Easier to test

49. VIPER | PROS
• Improved responsibility balance
• Well-defined contracts
• Smaller classes and methods
• Easier to test
• Easier to maintain and add new features

50. VIPER | PROS
• Improved responsibility balance
• Well-defined contracts
• Smaller classes and methods
• Easier to test
• Easier to maintain and add new features
• Possibility to use the same architecture between
iOS and Android projects

51. ANDROID ARCHITECTURE
COMPONENTES

52. SECTION | ARCHITECTURE COMPONENTS
"The most important thing you
should focus on is the separation of
concerns in your app.”
https://developer.android.com/topic/libraries/architecture/guide.html

54. View
Presenter?
Interactor
Model

55. SECTION | PRESENTER vs VIEWMODEL

56. SECTION | PRESENTER vs VIEWMODEL
• Both are responsible for preparing the data for
the UI

57. SECTION | PRESENTER vs VIEWMODEL
• Both are responsible for preparing the data for
the UI
• The Presenter has a reference to the view, while
ViewModel doesn’t

58. SECTION | PRESENTER vs VIEWMODEL
• Both are responsible for preparing the data for
the UI
• The Presenter has a reference to the view, while
ViewModel doesn’t
• The ViewModel enables data binding

59. SECTION | PRESENTER vs VIEWMODEL
• Both are responsible for preparing the data for
the UI
• The Presenter has a reference to the view, while
ViewModel doesn’t
• The ViewModel enables data binding
• The ViewModel provides observable data to the
view

60. SECTION | ARCHITECTURE COMPONENTS
"If your UI is complex, consider creating a
Presenter class to handle UI modifications.
This is usually overkill, but might make
your UIs easier to test."

62. VIPER | CONCLUSION
"It is impossible to have
one way of writing apps
that will be the best for
every scenario. (…) If you
already have a good way
of writing Android apps,
you don't need to change."

63. https://github.com/arctouch-gabrielzandavalle/tmdbviper

64. OBRIGADO
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