Advanced #6 clean architecture
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The document discusses Clean Architecture and provides an example of implementing it using a Movie Night app. It describes separating the app into Presentation, Data, and Domain layers with specific responsibilities. The Domain layer contains entities, use cases, and interfaces. The Data layer encapsulates data sources and mappers. The Presentation layer connects everything using ViewModels, LiveData, and observing lifecycle changes. It demonstrates how data flows from the Data layer through UseCases to the Presentation layer and updates the UI.
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Advanced #6 clean architecture
- 1. Clean Architecture: A Guided Tour Yossi Segev Tech Lead @ Kin Ecosystem @yossisegev yossisegev.com
- 2. Clean Architecture: A Guided Tour Yossi Segev Tech Lead @ Kin Ecosystem @yossisegev yossisegev.com
- 3. Why are we obsessed with architecture?
- 4. We want to be able to REACT TO CHANGES quickly & efficiently
- 5. Good architecture is •Easy to maintain / expand upon •Easy to test •Easy to understand
- 6. Keep in mind •Architecture is dynamic and ever-evolving •There are always several solutions to every problem •Every architecture decision is a trade-off •There is no such thing as “the perfect architecture”
- 8. The Layers Principle Layer C Layer B Layer A DependenciesFlow << Detailed << Generic
- 9. Movie Night app layers Presentation Data Domain DependenciesFlow
- 10. Movie Night app layers Presentation Data Domain •UI •Presenters •Dependency Injection •Web API •Storage (DB/In-Mem) •Use cases •Interfaces •Domain Entities DependenciesFlow
- 11. Modules as layers *Not by dependency flow order
- 13. Movie Night app layers Presentation Data Domain •UI •Presenters •Dependency Injection •Web API •Storage (DB/In-Mem) •Use cases •Interfaces •Domain Entities DependenciesFlow
- 14. The Domain Layer •The baseline of the application •Describes what the application is / what it can do •Generic code
- 15. • Domain Entities • Use cases • Interfaces The Domain Layer
- 16. Domain Entities • Simple data containers • The basic building blocks of our application • Acts as common language across the application
- 18. MovieEntity.kt data class MovieEntity( var id: Int = 0, var title: String, var overview: String? = null, var voteCount: Int = 0 // ... )
- 19. • Domain Entities • Use cases • Interfaces The Domain Layer
- 20. Use Case Encapsulates a single, very specific task to be performed
- 22. UseCase.kt abstract class UseCase<T>() { abstract fun create(): Observable<T> fun observable(): Observable<T> { return create().compose(t) } }
- 23. UseCase.kt abstract class UseCase<T>() { abstract fun create(): Observable<T> fun observable(): Observable<T> { return create().compose(t) } }
- 24. UseCase.kt abstract class UseCase<T>(t: ObservableTransformer) { abstract fun create(): Observable<T> fun observable(): Observable<T> { return create().compose(t) } }
- 25. UseCase.kt abstract class UseCase<T>(t: ObservableTransformer) { abstract fun create(): Observable<T> fun observable(): Observable<T> { return create().compose(t) } }
- 26. UseCase.kt abstract class UseCase<T>(t: ObservableTransformer) { abstract fun create(): Observable<T> fun observable(): Observable<T> { return create().compose(t) } }
- 27. Using a UseCase
- 28. Using a UseCase myUseCase .observable() .subscribe( { data -> // Do something with the data }, { throwable -> // Handle errors } )
- 29. Using a UseCase myUseCase .observable() .subscribe( { data -> // Do something with the data }, { throwable -> // Handle errors } )
- 30. Using a UseCase myUseCase .observable() .subscribe( { data -> // Do something with the data }, { throwable -> // Handle errors } )
- 31. Using a UseCase myUseCase .observable() .subscribe( { data -> // Do something with the data }, { throwable -> // Handle errors } )
- 33. GetPopularMovies.kt class GetPopularMovies(t: Transformer, repo: MoviesRepo) :UseCase<List<MovieEntity>>(t) { override fun create(): Observable<List<MovieEntity>> { return repo.getMovies() } }
- 34. GetPopularMovies.kt class GetPopularMovies(t: Transformer, repo: MoviesRepo) :UseCase<List<MovieEntity>>(t) { override fun create(): Observable<List<MovieEntity>> { return repo.getMovies() } }
- 35. GetPopularMovies.kt class GetPopularMovies(t: Transformer, repo: MoviesRepo) :UseCase<List<MovieEntity>>(t) { override fun create(): Observable<List<MovieEntity>> { return repo.getMovies() } }
- 36. MoviesRepo.kt interface MoviesRepo { fun getMovies(): Observable<List<MovieEntity>> // . . . }
- 37. • Domain Entities • Use cases • Interfaces The Domain Layer
- 38. Interfaces • Dictates the contract the upper layers must follow • Ensures the application core functionality will hold true, regardless implementation details changes
- 39. Moving up!
- 40. The Data Layer
- 41. Movie Night app layers Data Domain •Web API •Storage (DB/In-Mem) •Domain Entities •Interfaces •Use cases
- 42. The Data Layer •Caching mechanism •Database •Networking •Mappers
- 43. The Data Layer Encapsulates any knowledge regarding where the application data is coming from and how it is stored
- 45. The Data Layer •Caching mechanism •Database •Networking •Mappers
- 46. Mappers Maps Class A to Class B
- 47. Mapper.kt abstract class Mapper<in E, T> { abstract fun mapFrom(from: E): T // ... }
- 48. MyMapper.kt class MyMapper: Mapper<MovieEntity, MovieData>() { override fun mapFrom(from: MovieEntity): MovieData { return MovieData( id = from.id, originalTitle = from.originalTitle, releaseDate = from.releaseDate, overview = from.overview // ... ) } }
- 49. MyMapper.kt class MyMapper: Mapper<MovieEntity, MovieData>() { override fun mapFrom(from: MovieEntity): MovieData { return MovieData( id = from.id, originalTitle = from.originalTitle, releaseDate = from.releaseDate, overview = from.overview // ... ) } }
- 50. MyMapper.kt class MyMapper: Mapper<MovieEntity, MovieData>() { override fun mapFrom(from: MovieEntity): MovieData { return MovieData( id = from.id, originalTitle = from.originalTitle, releaseDate = from.releaseDate, overview = from.overview // ... ) } }
- 51. Why do we need Mappers?
- 52. import android.arch.persistence.room.Entity import android.arch.persistence.room.PrimaryKey import com.google.gson.annotations.SerializedName @Entity(tableName = "movies") data class MovieData( @PrimaryKey var id: Int = -1, @SerializedName("original_title") var originalTitle: String // ... ) MovieData.kt
- 53. Why do we need Mappers? The Data layer contains details we want to hide.
- 59. Summarising the Data Layer •Contains concrete implementations of data providers •Act as a boundary, encapsulates data providers details and hide them from the “outside world”.
- 60. Movie Night app layers Presentation Data Domain •UI •Presenters •Dependency Injection •Web API •Storage (DB/In-Mem) •Use cases •Interfaces •Domain Entities DependenciesFlow
- 62. The Presentation Layer Connects all the different pieces into a single, functioning unit that is the application
- 63. The Presentation Layer •Activities, Fragments •View States •Presenters •Mappers •Dependency Injection
- 65. Why ViewModel & LiveData? Lifecycle awareness.
- 66. ViewModel 101 class MainActivity : AppCompatActivity() { val vm = ViewModelProviders .of(lifecycleOwner) .get(MyViewModel::class.java) }
- 67. ViewModel 101 class MainActivity : AppCompatActivity() { // Creation val vm = ViewModelProviders .of(lifecycleOwner) .get(MyViewModel::class.java) }
- 68. ViewModel 101 class MainActivity : AppCompatActivity() { // Creation val vm = ViewModelProviders .of(lifecycleOwner) .get(MyViewModel::class.java) }
- 69. ViewModel 101 class MainActivity : AppCompatActivity() { // Creation val vm = ViewModelProviders .of(lifecycleOwner) .get(MyViewModel::class.java) }
- 70. ViewModel 101 class MyViewModel: ViewModel() { // ... override fun onCleared() { super.onCleared() // Clear resources etc... } }
- 71. LiveData 101
- 72. LiveData 101 // Creating val liveData = MutableLiveData<String>() // Observing liveData.observe(lifecycleOwner, Observer { data -> // do something with data… }) // Updating value liveData.value = "Hello world!"
- 73. LiveData 101 // Creating val liveData = MutableLiveData<String>() // Observing liveData.observe(lifecycleOwner, Observer { data -> // do something with data… }) // Updating value liveData.value = "Hello world!"
- 74. LiveData 101 // Creating val liveData = MutableLiveData<String>() // Observing liveData.observe(lifecycleOwner, Observer { data -> // do something with data… }) // Updating value liveData.value = "Hello world!"
- 76. The Presentation Layer •Activities, Fragments •View States •Presenters •Mappers •Dependency Injection
- 78. ViewState Represents the state of a view
- 79. PopularViewState.kt data class PopularViewState( var loading: Boolean = true, var movies: List<MovieEntity>? = null )
- 82. PopularViewModel
- 83. class PopularViewModel(val useCase: GetPopularMovies) : BaseViewModel() { var viewState: MutableLiveData<PopularViewState> init { viewState.value = PopularViewState() } PopularViewModel.kt
- 84. class PopularViewModel(val useCase: GetPopularMovies) : BaseViewModel() { var viewState: MutableLiveData<PopularViewState> init { viewState.value = PopularViewState() } PopularViewModel.kt
- 85. class PopularViewModel(val useCase: GetPopularMovies) : BaseViewModel() { var viewState: MutableLiveData<PopularViewState> init { // Sets the initial view state viewState.value = PopularViewState() } // ... PopularViewModel.kt
- 86. getPopularMovies .observable() .subscribe({ movies -> val newState = viewState.value .copy(loading = false, movies = movies) this.viewState.value = newState }, { throwable -> // Handle errors })) PopularViewModel.kt
- 87. getPopularMovies .observable() .subscribe({ movies -> }, { throwable -> // Handle errors })) PopularViewModel.kt
- 88. getPopularMovies .observable() .subscribe({ movies -> val newState = viewState.value .copy(loading = false, movies = movies) }, { throwable -> // Handle errors })) PopularViewModel.kt
- 89. getPopularMovies .observable() .subscribe({ movies -> val newState = viewState.value .copy(loading = false, movies = movies) viewState.value = newState }, { throwable -> // Handle errors })) PopularViewModel.kt
- 90. PopularViewModel.kt val disposable = getPopularMovies .observable() .subscribe( /* ... */ ) addDisposable(disposable)
- 93. PopularMoviesFragment.kt val viewModel = ViewModelProviders .of(this, factory) .get(PopularViewModel::class.java) // ... viewModel.viewState .observe(this, Observer { state -> handleViewState(state) })
- 94. PopularMoviesFragment.kt val viewModel = ViewModelProviders .of(this, factory) .get(PopularViewModel::class.java) // ... viewModel.viewState .observe(this, Observer { state -> handleViewState(state) })
- 95. PopularMoviesFragment.kt fun handleViewState(state: PopularViewState) { if (state.loading) { // Show or hide the progressBar } state.movies?.let { // Show movies } }
- 96. The Presentation Layer •Activities, Fragments •View States •Presenters •Mappers •Dependency Injection
- 97. Dependency Injection • Wires everything across the application • Providing concrete implementations
- 98. Summary