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Clean Architecture

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What is Architecture?

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• MVP • Realm • RxJava • Dagger • Retrofit • Gson

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• MVP • Realm • RxJava • Dagger • Retrofit • Gson NO!

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Tools • MVP • Realm • RxJava • Dagger • Retrofit • Gson

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Screaming Architecture

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No content

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No content

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Architecture is about intent

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Architecture is about use cases

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Entities Use Cases Controllers Gateways Presenters Devices Web DB UI External Interfaces Enterprise Business Rules Application Business Rules Interface Adapters Frameworks & Drivers Presenter Controller Use Case Input Port Use Case Interactor Use Case Output Port Flow of Control

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Entities Use Cases Controllers Gateways Presenters Devices Web DB UI External Interfaces Enterprise Business Rules Application Business Rules Interface Adapters Frameworks & Drivers Presenter Controller Use Case Input Port Use Case Interactor Use Case Output Port Flow of Control

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Use Cases Controllers Gateways Presenters Devices Web DB UI External Interfaces Enterprise Business Rules Application Business Rules Interface Adapters Frameworks & Drivers Presenter Controller Use Case Input Port Use Case Interactor Use Case Output Port Flow of Control

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Controllers Gateways Presenters Devices Web DB UI External Interfaces Enterprise Business Rules Application Business Rules Interface Adapters Frameworks & Drivers Presenter Controller Use Case Input Port Use Case Interactor Use Case Output Port Flow of Control

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Devices Web DB UI External Interfaces Enterprise Business Rules Application Business Rules Interface Adapters Frameworks & Drivers Presenter Controller Use Case Input Port Use Case Interactor Use Case Output Port Flow of Control

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POLICIES The Dependency Rule MECHANISMS

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POLICIES The Dependency Rule MECHANISMS

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POLICIES The Dependency Rule MECHANISMS

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POLICIES The Dependency Rule MECHANISMS

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POLICIES The Dependency Rule MECHANISMS

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Independent of Frameworks

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Testable

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Independent of UI

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Independent of Database

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Independent of External Agency

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Decoupled

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A Clean App

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github.com/pardom/CleanNews

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Entities Use cases Data sources, Presentation models Delivery mechanisms, databases Core App Presentation Data Android Desktop CleanNews ├── android ├── app ├── core ├── data ├── desktop └── presentation

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Entities Use cases Data sources, Presentation models Delivery mechanisms, databases Core App Presentation Data Android Desktop CleanNews ├── android ├── app ├── core ├── data ├── desktop └── presentation

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Entities Use cases Data sources, Presentation models Delivery mechanisms, databases App Presentation Data Android Desktop CleanNews ├── android ├── app ├── core ├── data ├── desktop └── presentation

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Entities Use cases Data sources, Presentation models Delivery mechanisms, databases Presentation Data Android Desktop CleanNews ├── android ├── app ├── core ├── data ├── desktop └── presentation

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Entities Use cases Data sources, Presentation models Delivery mechanisms, databases Android Desktop CleanNews ├── android ├── app ├── core ├── data ├── desktop └── presentation

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app/src/main/kotlin/clean/news/app/
 ├── item
 │ ├── GetChildren
 │ ├── GetItemById
 │ ├── GetItemsByListType
 │ └── SaveItem
 └── user
 ├── GetUserById
 └── SaveUser

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app/src/main/kotlin/clean/news/app/
 ├── item
 │ ├── GetChildren
 │ ├── GetItemById
 │ ├── GetItemsByListType
 │ └── SaveItem
 └── user
 ├── GetUserById
 └── SaveUser

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Entities

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“An entity is something that exists as itself, as a subject or as an object, actually or potentially, concretely or abstractly, physically or not.”

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apply plugin: 'java'
 
 dependencies { 
 } Core

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core/src/main/kotlin/clean/news/core/entity/
 ├── Item.kt
 └── User.kt

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data class Item(
 val id: Long,
 val type: Type,
 val by: String?,
 val time: Date,
 val text: String?,
 val url: String?,
 val title: String?) {
 
 enum class Type(val canComment: Boolean) {
 JOB(false), STORY(true), COMMENT(true), POLL(true), POLLOPT(true), NONE(false)
 }
 }

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data class Item(
 val id: Long,
 val type: Type,
 val by: String?,
 val time: Date,
 val text: String?,
 val url: String?,
 val title: String?) {
 
 enum class Type(val canComment: Boolean) {
 JOB(false), STORY(true), COMMENT(true), POLL(true), POLLOPT(true), NONE(false)
 }
 }

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data class User(
 val id: String,
 val delay: Int,
 val created: Date,
 val karma: Int,
 val about: String,
 val submitted: List
 )

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Entities • Contain enterprise wide business rules • Encapsulate high-level rules • Unaffected by external layers

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Use Cases

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“A use case is a list of actions or event steps, typically defining the interactions between a role and a system, to achieve a goal.”

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Title (goal) Primary Actor: …
 Scope: …
 Level: … (Story): the body of the use case is simply a paragraph or two of text, informally describing what happens.

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Retrieve story details Primary Actor: Reader
 Scope: A Hacker News client
 Level: User goal The reader invokes the client to retrieve the details for a story. This includes the children of a story, namely the comments.

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apply plugin: 'java'
 
 dependencies {
 compile project(':core')
 } Core App

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Entities Use Cases Controllers Gateways Presenters Devices Web DB UI External Interfaces Enterprise Business Rules Application Business Rules Interface Adapters Frameworks & Drivers Presenter Controller Use Case Input Port Use Case Interactor Use Case Output Port Flow of Control

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Presenter Controller Use Case Input Port Use Case Interactor Use Case Output Port Flow of Control

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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Request Model Response Model Use Case Boundary Boundary Presentation Model

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interface UseCase {
 
 fun execute(request: I): Observable
 
 interface Request
 
 interface Response
 
 }

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interface UseCase {
 
 fun execute(request: I): Observable
 
 interface Request
 
 interface Response
 
 }

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interface UseCase {
 
 fun execute(request: I): Observable
 
 interface Request
 
 interface Response
 
 }

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interface UseCase {
 
 fun execute(request: I): Observable
 
 interface Request
 
 interface Response
 
 }

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interface UseCase {
 
 fun execute(request: I): Observable
 
 interface Request
 
 interface Response
 
 }

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interface UseCase {
 
 fun execute(request: I): Observable
 
 interface Request
 
 interface Response
 
 }

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interface UseCase {
 
 fun execute(request: I): Observable
 
 interface Request
 
 interface Response
 
 }

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interface UseCase {
 
 fun execute(request: I): Observable
 
 interface Request
 
 interface Response
 
 }

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interface UseCase {.
 
 fun execute(): Observable
 
 }.

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interface UseCase1 {.
 
 fun execute(arg1: A): Observable
 
 }.

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interface UseCase2 {.
 
 fun execute(arg1: A, arg2: B): Observable
 
 }.

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interface UseCase3 {.
 
 fun execute(arg1: A, arg2: B, arg3: C): Observable
 
 }.

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app/src/main/kotlin/clean/news/app/
 └── usecase
 ├── item
 │ ├── GetChildren.kt
 │ ├── GetItemById.kt
 │ ├── GetItemsByListType.kt
 │ └── SaveItem.kt
 └── user
 ├── GetUserById.kt
 └── SaveUser.kt

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GetChildren.Request GetChildren.Response GetChildren ItemNetworkDataSource ItemRetrofitDataSource ItemDetailsViewModel

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GetChildren.Request GetChildren.Response GetChildren ItemNetworkDataSource ItemRetrofitDataSource ItemDetailsViewModel

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GetChildren.Request GetChildren.Response GetChildren ItemNetworkDataSource ItemRetrofitDataSource ItemDetailsViewModel

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GetChildren.Request GetChildren.Response GetChildren ItemNetworkDataSource ItemRetrofitDataSource ItemDetailsViewModel

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GetChildren.Request GetChildren.Response GetChildren ItemNetworkDataSource ItemRetrofitDataSource ItemDetailsViewModel

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GetChildren.Request GetChildren.Response GetChildren ItemNetworkDataSource ItemRetrofitDataSource ItemDetailsViewModel

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GetChildren.Request GetChildren.Response GetChildren ItemNetworkDataSource ItemRetrofitDataSource ItemDetailsViewModel

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class GetChildren @Inject constructor(
 private val network: ItemNetworkDataSource) : UseCase {
 
 override fun execute(request: Request): Observable {
 return network.getChildren(request.item)
 .map { Response(it) }
 }
 
 class Request(val item: Item) : UseCase.Request
 
 class Response(val items: List) : UseCase.Response
 }

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class GetChildren @Inject constructor(
 private val network: ItemNetworkDataSource) : UseCase {
 
 override fun execute(request: Request): Observable {
 return network.getChildren(request.item)
 .map { Response(it) }
 }
 
 class Request(val item: Item) : UseCase.Request
 
 class Response(val items: List) : UseCase.Response
 }

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class GetChildren @Inject constructor(
 private val network: ItemNetworkDataSource) : UseCase {
 
 override fun execute(request: Request): Observable {
 return network.getChildren(request.item)
 .map { Response(it) }
 }
 
 class Request(val item: Item) : UseCase.Request
 
 class Response(val items: List) : UseCase.Response
 }

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class GetChildren @Inject constructor(
 private val network: ItemNetworkDataSource) : UseCase {
 
 override fun execute(request: Request): Observable {
 return network.getChildren(request.item)
 .map { Response(it) }
 }
 
 class Request(val item: Item) : UseCase.Request
 
 class Response(val items: List) : UseCase.Response
 }

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class GetChildren @Inject constructor(
 private val network: ItemNetworkDataSource) : UseCase {
 
 override fun execute(request: Request): Observable {
 return network.getChildren(request.item)
 .map { Response(it) }
 }
 
 class Request(val item: Item) : UseCase.Request
 
 class Response(val items: List) : UseCase.Response
 }

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class GetChildren @Inject constructor(
 private val network: ItemNetworkDataSource) : UseCase {
 
 override fun execute(request: Request): Observable {
 return network.getChildren(request.item)
 .map { Response(it) }
 }
 
 class Request(val item: Item) : UseCase.Request
 
 class Response(val items: List) : UseCase.Response
 }

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class GetChildren @Inject constructor(
 private val network: ItemNetworkDataSource) : UseCase {
 
 override fun execute(request: Request): Observable {
 return network.getChildren(request.item)
 .map { Response(it) }
 }
 
 class Request(val item: Item) : UseCase.Request
 
 class Response(val items: List) : UseCase.Response
 }

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app/src/main/kotlin/clean/news/app/
 └── data
 ├── DataSource.kt
 ├── item
 │ ├── ItemDataSource.kt
 │ ├── ItemDiskDataSource.kt
 │ ├── ItemMemoryDataSource.kt
 │ └── ItemNetworkDataSource.kt
 └── user
 ├── UserDataSource.kt
 ├── UserDiskDataSource.kt
 ├── UserMemoryDataSource.kt
 └── UserNetworkDataSource.kt

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interface DataSource {
 fun getAll(): Observable>
 
 fun getById(id: ID): Observable
 
 fun save(t: T): Observable
 }

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interface ItemDataSource : DataSource {
 fun getItems(listType: ListType): Observable>
 
 fun getChildren(item: Item): Observable>
 }

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interface ItemDiskDataSource : ItemDataSource interface ItemMemoryDataSource : ItemDataSource interface ItemNetworkDataSource : ItemDataSource

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Use Cases • Contain application specific business rules • Orchestrate the flow of data to and from entities • Unaffected by external systems like database or UI

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Interface Adapters

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“a design pattern that allows the interface of an existing class to be used as another interface.”

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apply plugin: 'java'
 
 dependencies {
 compile project(':app')
 } Core App Presentation Data

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ItemNetworkDataSource GetChildren ItemRetrofitDataSource ItemDetailViewModel

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ItemNetworkDataSource GetChildren ItemRetrofitDataSource ItemDetailViewModel

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ItemNetworkDataSource GetChildren ItemRetrofitDataSource ItemDetailViewModel

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ItemNetworkDataSource GetChildren ItemRetrofitDataSource ItemDetailViewModel

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ItemNetworkDataSource GetChildren ItemRetrofitDataSource ItemDetailViewModel

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presentation/src/main/kotlin/clean/news/presentation/model/
 ├── Model.kt
 ├── item
 │ ├── ItemDetailViewModel.kt
 │ ├── ItemListViewModel.kt
 │ └── ItemUrlViewModel.kt
 └── main
 └── MainViewModel.kt

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class ItemDetailViewModel @Inject constructor(
 private val getChildren: GetChildren,
 private val item: Item) : Model {
 
 private val children = getChildren.execute(Request(item))
 .map { it.items }
 .replay(1)
 .autoConnect()
 }

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class ItemDetailViewModel @Inject constructor(
 private val getChildren: GetChildren,
 private val item: Item) : Model {
 
 private val children = getChildren.execute(Request(item))
 .map { it.items }
 .replay(1)
 .autoConnect()
 }

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class ItemDetailViewModel @Inject constructor(
 private val getChildren: GetChildren,
 private val item: Item) : Model {
 
 private val children = getChildren.execute(Request(item))
 .map { it.items }
 .replay(1)
 .autoConnect()
 }

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data/src/main/kotlin/clean/news/data/
 ├── lru
 │ ├── ItemLruDataSource.kt
 │ └── UserLruDataSource.kt
 ├── retrofit
 │ ├── ItemRetrofitDataSource.kt
 │ └── UserRetrofitDataSource.kt
 └── sqlite
 ├── ItemSqliteDataSource.kt
 └── UserSqliteDataSource.kt

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class ItemRetrofitDataSource @Inject constructor(
 private val itemService: ItemService) : ItemNetworkDataSource {
 
 override fun getById(id: Long): Observable {
 return itemService.getById(id)
 }
 }

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class ItemRetrofitDataSource @Inject constructor(
 private val itemService: ItemService) : ItemNetworkDataSource {
 
 override fun getById(id: Long): Observable {
 return itemService.getById(id)
 }
 }

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class ItemRetrofitDataSource @Inject constructor(
 private val itemService: ItemService) : ItemNetworkDataSource {
 
 override fun getById(id: Long): Observable {
 return itemService.getById(id)
 }
 }

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interface ItemService { 
 @GET("item/{item_id}.json")
 fun getById(@Path("item_id") id: Long): Observable 
 }

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class ItemRetrofitDataSource @Inject constructor(
 private val itemService: ItemService) : ItemNetworkDataSource {
 
 override fun getById(id: Long): Observable {
 return itemService.getById(id)
 }
 }

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Interface Adapters • Convert data between uses cases and external agencies • MVC, MVP, MVVM, RPM implementation • Database adapter • Network adapter

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Frameworks and Drivers

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“a universal, reusable software environment that provides particular functionality as part of a larger software platform to facilitate development”

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apply plugin: 'com.android.application'
 
 dependencies {
 compile project(':presentation')
 compile project(':data')
 } Core App Presentation Data Android Desktop

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class ItemDetailView : RelativeLayout { 
 @Inject
 lateinit var model: ItemDetailViewModel
 
 @JvmOverloads
 constructor(...) : super(context, attrs, defStyle) {
 ComponentService.getService(context)?.inject(this)
 } }

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class ItemDetailView : RelativeLayout {
 @Inject
 lateinit var model: ItemDetailViewModel
 
 @JvmOverloads
 constructor(...) : super(context, attrs, defStyle) {
 ComponentService.getService(context)?.inject(this)
 } }

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class ItemDetailView : RelativeLayout { 
 @Inject
 lateinit var model: ItemDetailViewModel
 
 @JvmOverloads
 constructor(...) : super(context, attrs, defStyle) {
 ComponentService.getService(context)?.inject(this)
 } }

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@Module
 class DataModule { 
 @Provides
 @ApplicationScope
 fun itemService(retrofit: Retrofit): ItemService {
 return retrofit.create(ItemService::class.java)
 }
 
 @Provides
 @ApplicationScope
 fun itemNetworkDataSource(itemService: ItemService): ItemNetworkDataSource {
 return ItemRetrofitDataSource(itemService)
 }
 
 }

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@Module
 class DataModule { 
 @Provides
 @ApplicationScope
 fun itemService(retrofit: Retrofit): ItemService {
 return retrofit.create(ItemService::class.java)
 }
 
 @Provides
 @ApplicationScope
 fun itemNetworkDataSource(itemService: ItemService): ItemNetworkDataSource {
 return ItemRetrofitDataSource(itemService)
 }
 
 }

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@Module
 class DataModule { 
 @Provides
 @ApplicationScope
 fun itemService(retrofit: Retrofit): ItemService {
 return retrofit.create(ItemService::class.java)
 }
 
 @Provides
 @ApplicationScope
 fun itemNetworkDataSource(itemService: ItemService): ItemNetworkDataSource {
 return ItemRetrofitDataSource(itemService)
 }
 
 }

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override fun onAttachedToWindow() {
 super.onAttachedToWindow()
 val sinks = model.setUp(Sources(
 toolbar.navigationClicks(),
 Observable.empty(),
 toolbar.itemClicks()
 .filter {it.itemId == R.id.item_share }
 .map { Unit }
 ))
 }

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override fun onAttachedToWindow() {
 super.onAttachedToWindow()
 val sinks = model.setUp(Sources(
 toolbar.navigationClicks(),
 Observable.empty(),
 toolbar.itemClicks()
 .filter {it.itemId == R.id.item_share }
 .map { Unit }
 ))
 }

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Frameworks and Drivers • Glue code to communicate inwards • Delivery mechanism • Dependency providers

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POLICIES MECHANISMS

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Resources • https://github.com/pardom/CleanNews • https://blog.8thlight.com/uncle-bob/2012/08/13/the-clean-architecture.html • https://cleancoders.com/episode/clean-code-episode-7/show

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Questions? @pardom michaelpardo.com