Why do we need Clean Architecture? Igor Wojda @igorwojda 

About me 

Why do we need good architecture? 1519 1520 1521 1522 1523 1524 

MVP View Presenter Model 

MVP + Repository View Presenter Repository DataSource DataSource 

“ We should think about our applications as group of use cases that describe the intent of the application and group of plugins that give those uses cases access to outside word. Uncle Bob 

Why Clean Architecture? ◦ Independent of libraries & frameworks ◦ Independent of UI ◦ Independent of data sources Business Logic UI Frameworks Data sources 

UI Data source Presenter Repository Use case Dependency rule Entity 

Dependency rule UI Data source Presenter Repository Use case Entity Dependency rule Data Flow 

UI Data source Presenter Repository Use case Entity Layers 

Presentation Layer Domain Layer Data Layer Layers 

Presentation Layer Data Layer Presenter View Use case Entity Repository Network Data Source Disk Data Source Layers Domain Layer Dependencies 

Dependency inversion UseCase Repository • Define interface • Class Repository implements this interface • Class Repository is injected into class UseCase UseCase Repository 

Presentation Layer Domain Layer Data Layer Presenter View Use case Repository Network Data Source Disk Data Source Layers Abstractions Entity 

Data model data class PatientModel( val id: String, val firstName: String, val lastName: String, val dateOfBirth: String ) 

Data model (GSON) data class PatientModel( @SerializedName("id") val id: String, @SerializedName("first_name") val firstName: String, @SerializedName("last_name") val lastName: String, @SerializedName("date_of_birth") val dateOfBirth: String ) 

Data model (GSON + Room) @Entity(tableName = "patients") data class PatientModel( @SerializedName("id") @PrimaryKey val id: String, @SerializedName("first_name") @ColumnInfo(name = "first_name") val firstName: String, @SerializedName("last_name") @ColumnInfo(name = "last_name") val lastName: String, @SerializedName("date_of_birth") @ColumnInfo(name = "date_of_birth") val dateOfBirth: String ) 

Data model (GSON + Room + Getters) @Entity(tableName = "patients") data class PatientModel( @SerializedName("id") @PrimaryKey val id: String, @SerializedName("first_name") @ColumnInfo(name = "first_name") val firstName: String, @SerializedName("last_name") @ColumnInfo(name = "last_name") val lastName: String, @SerializedName("date_of_birth") @ColumnInfo(name = "date_of_birth") val dateOfBirth: String ) { private val UNDER_AGE_LIMIT = 16 val fullName = "$firstName $lastName" val adult = DateTime.parse(dateOfBirth) .plusYears(UNDER_AGE_LIMIT) .isAfter(DateTime.now()) } 

Data models Presentation Layer Domain Layer Data Layer PatientPresentation Model Patient PatientNetworkModel PatientRoomModel PatientNetworkMapper PatientRoomMapper PatientViewMapper 

Separate data model data class PatientNetworkModel( @SerializedName("id") val id: String, @SerializedName("first_name") val firstName: String, @SerializedName("last_name") val lastName: String, @SerializedName("date_of_birth") val dateOfBirth: String ) Data Layer 

Separate data model Data Layer @Entity(tableName = "patients") data class PatientRoomModel( @PrimaryKey val id: String, @ColumnInfo(name = "first_name") val firstName: String, @ColumnInfo(name = "last_name") val lastName: String, @ColumnInfo(name = "date_of_birth") val dateOfBirth: String ) 

Separate data model Domain Layer data class Patient( val id: String, val firstName: String, val lastName: String, val dateOfBirth: DateTime ) 

Separate data model data class PatientPresentationModel( val fullName: String, val adult: Boolean, val dateOfBirth: String ) Presentation Layer 

Data representations Presentation Layer Domain Layer Data Layer 

Data representations Presentation Layer Domain Layer Data Layer "20171026T170000Z" DateTime "26th Oct 2017" 1509037200 

Mapper interface Mapper { fun map(from: FROM): TO } class PatientNetworkModelMapper : Mapper { override fun map(patientNetworkModel: PatientNetworkModel) = Patient( id = patientNetworkModel.id, firstName = patientNetworkModel.firstName, lastName = patientNetworkModel.lastName, dateOfBirth = DateTime.parse(patientNetworkModel.dateOfBirth) ) } 

Mapper interface Mapper { fun map(from: FROM): TO } class PatientNetworkModelMapper : Mapper { override fun map(patientNetworkModel: PatientNetworkModel) = Patient( id = patientNetworkModel.id, firstName = patientNetworkModel.firstName, lastName = patientNetworkModel.lastName, dateOfBirth = DateTime.parse(patientNetworkModel.dateOfBirth) ) } 

Mapper interface Mapper { fun map(from: FROM): TO } class PatientNetworkModelMapper : Mapper { override fun map(patientNetworkModel: PatientNetworkModel) = Patient( id = patientNetworkModel.id, firstName = patientNetworkModel.firstName, lastName = patientNetworkModel.lastName, dateOfBirth = DateTime.parse(patientNetworkModel.dateOfBirth) ) } 

Presentation Layer Domain Layer Data Layer Presenter View Use case Entity Repository Network Data Source Disk Data Source Implementations Abstractions 

Presenter class PatientsPresenter @Inject constructor( val getPatientsUseCase: PatientsUseCase, val mapper: PatientPresentationMapper) : BasePresenter, PatientsContract.Presenter { override fun onAttachView() { getPatientsUseCase.execute(PatientSubscriber()) } inner class PatientSubscriber : DisposableSingleObserver>() { override fun onSuccess(patients: List) { when { patients.isEmpty -> view?.showEmptyState() else -> view?.showPatients(Patients.map { patientMapper::map }) } } override fun onError(exception: Throwable) { view?.showErrorState() } //… } } 

Presenter class PatientsPresenter @Inject constructor( val getPatientsUseCase: PatientsUseCase, val mapper: PatientPresentationMapper) : BasePresenter, PatientsContract.Presenter { override fun onAttachView() { getPatientsUseCase.execute(PatientSubscriber()) } inner class PatientSubscriber : DisposableSingleObserver>() { override fun onSuccess(patients: List) { when { patients.isEmpty -> view?.showEmptyState() else -> view?.showPatients(mapper.map { patientMapper::map }) } } override fun onError(exception: Throwable) { view?.showErrorState() } //… } } 

Presenter class PatientsPresenter @Inject constructor( val getPatientsUseCase: PatientsUseCase, val mapper: PatientPresentationMapper) : BasePresenter, PatientsContract.Presenter { override fun onAttachView() { getPatientsUseCase.execute(PatientSubscriber()) } inner class PatientSubscriber : DisposableSingleObserver>() { override fun onSuccess(patients: List) { when { patients.isEmpty -> view?.showEmptyState() else -> view?.showPatients(mapper.map { patientMapper::map }) } } override fun onError(exception: Throwable) { view?.showErrorState() } //… } } 

Presenter class PatientsPresenter @Inject constructor( val getPatientsUseCase: PatientsUseCase, val mapper: PatientPresentationMapper) : BasePresenter, PatientsContract.Presenter { override fun onAttachView() { getPatientsUseCase.execute(PatientSubscriber()) } inner class PatientSubscriber : DisposableSingleObserver>() { override fun onSuccess(patients: List) { when { patients.isEmpty -> view?.showEmptyState() else -> view?.showPatients(mapper.map { patientMapper::map }) } } override fun onError(exception: Throwable) { view?.showErrorState() } //… } } 

Presenter class PatientsPresenter @Inject constructor( val getPatientsUseCase: PatientsUseCase, val mapper: PatientPresentationMapper) : BasePresenter, PatientsContract.Presenter { override fun onAttachView() { getPatientsUseCase.execute(PatientSubscriber()) } inner class PatientSubscriber : DisposableSingleObserver>() { override fun onSuccess(patients: List) { when { patients.isEmpty -> view?.showEmptyState() else -> view?.showPatients(mapper.map { patientMapper::map }) } } override fun onError(exception: Throwable) { view?.showErrorState() } //… } } 

Presentation Layer Domain Layer Data Layer Presenter View Use case Entity Repository Network Data Source Disk Data Source Layers Abstractions 

Use case (Interactor) class PatientsUseCase @Inject constructor(val patientRepository: PatientRepository, val schedulers: Schedulers) { fun execute(): Single> = patientRepository.getPatients() .observeOn(schedulers.main) .subscribeOn(schedulers.io) .filter { it.adult } } 

Use case (Interactor) class PatientsUseCase @Inject constructor(val patientRepository: PatientRepository, val schedulers: Schedulers) { fun execute(): Single> = patientRepository.getPatients() .observeOn(schedulers.main) .subscribeOn(schedulers.io) .filter { it.adult } } 

Use case (Interactor) class PatientsUseCase @Inject constructor(val patientRepository: PatientRepository, val schedulers: Schedulers) { fun execute(): Single> = patientRepository.getPatients() .observeOn(schedulers.main) .subscribeOn(schedulers.io) .filter { it.adult } } 

Presentation Layer Domain Layer Data Layer Presenter View Use case Entity Repository Network Data Source Disk Data Source Layers Abstractions 

class PatientDataRepository @Inject constructor(val diskDataStore: PatientDiskDataStore, val networkDataStore: PatientNetworkDataStore) : PatientRepository { val networkDataStoreWithSave = networkDataStore.doOnSuccess { saveToDisk(it) } fun getPatients(): Single> = Single.concat(diskDataStore, networkDataStoreWithSave) .takeFirst() fun saveToDisk() { /* … */ } } Repository 

class PatientDataRepository @Inject constructor(val diskDataStore: PatientDiskDataStore, val networkDataStore: PatientNetworkDataStore) : PatientRepository { val networkDataStoreWithSave = networkDataStore.doOnSuccess { saveToDisk(it) } fun getPatients(): Single> = Single.concat(diskDataStore, networkDataStoreWithSave) .takeFirst() fun saveToDisk() { /* … */ } } Repository PatientRepository PatientDataRepository: PatientRepository 

class PatientDataRepository @Inject constructor(val diskDataStore: PatientDiskDataStore, val networkDataStore: PatientNetworkDataStore) : PatientRepository { val networkDataStoreWithSave = networkDataStore.doOnSuccess { saveToDisk(it) } fun getPatients(): Single> = Single.concat(diskDataStore, networkDataStoreWithSave) .takeFirst() fun saveToDisk() { /* … */ } } Repository 

class PatientDataRepository @Inject constructor(val diskDataStore: PatientDiskDataStore, val networkDataStore: PatientNetworkDataStore) : PatientRepository { val networkDataStoreWithSave = networkDataStore.doOnSuccess { saveToDisk(it) } fun getPatients(): Single> = Single.concat(diskDataStore, networkDataStoreWithSave) .takeFirst() fun saveToDisk() { /* … */ } } Repository 

Data flow View Presenter Use case Repository Network Data Source SQLite Data Source Entity 

Modularity Presentation Layer Domain Layer Data Layer Presenter Business Logic View GridView Recycler View TabLayout BottomBar Patient Repository Tracking Repository SQLite Volley Firebase Firebase Room Retrofit MixPanel 

Testing Presentation Layer Domain Layer Data Layer Presenter Use case View Repository Network Data Source Entity Room Data Source 

Testing Presentation Layer Domain Layer Data Layer Mapper Mock RetrofitService Mock Mapper Mock Mock SQLite Data Source Mock Data Source Mock Repository Mock Presenter Mock Mapper Mock Mapper Mock Mapper Mock Entity Entity Entity View Mock Use Case Mock Mapper Mock 

Pros and cons Boilerplate code Not suitable for all projects Multiple ways to implement Independent of Frameworks and tools Well structured Maintainable Modular Testable Great for big teams Issues Benefits 

References Articles https://8thlight.com/blog/uncle-bob/2012/08/13/the-clean-architecture.html Talks https://youtu.be/Nsjsiz2A9mg https://youtu.be/3Mq5newPdck https://youtu.be/-sEmrJOk1uI https://youtu.be/su34EYeQ90E Android projects https://github.com/bufferapp/android-clean-architecture-boilerplate https://github.com/bufferapp/clean-architecture-components-boilerplate https://github.com/android10/Android-CleanArchitecture-Kotlin 

Thanks! ANY QUESTIONS? @igorwojda [email protected] 

Special thanks to SlidesCarnival who made and released these awesome presentation template for free. Credits