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Clean Architecture

Clean Architecture

A practical guide to making your code more readable, testable, and maintainable using clean architecture.

Michael Pardo

April 30, 2016
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  1. Clean Architecture

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  2. What is Architecture?

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  3. • MVP
    • Realm
    • RxJava
    • Dagger
    • Retrofit
    • Gson

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

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

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  6. Screaming Architecture

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  9. Architecture is about intent

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  10. Architecture is about use cases

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  11. 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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  12. 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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  13. 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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  14. 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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  15. 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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  16. POLICIES
    The Dependency Rule
    MECHANISMS

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  17. POLICIES
    The Dependency Rule
    MECHANISMS

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  18. POLICIES
    The Dependency Rule
    MECHANISMS

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  19. POLICIES
    The Dependency Rule
    MECHANISMS

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  20. POLICIES
    The Dependency Rule
    MECHANISMS

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  21. Independent of Frameworks

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  22. Testable

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  23. Independent of UI

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  24. Independent of Database

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  25. Independent of External Agency

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  26. Decoupled

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  27. A Clean App

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  28. github.com/pardom/CleanNews

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  29. 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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  30. 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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  31. 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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  32. 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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  33. Entities
    Use cases
    Data sources, Presentation models
    Delivery mechanisms, databases
    Android
    Desktop
    CleanNews
    ├── android
    ├── app
    ├── core
    ├── data
    ├── desktop
    └── presentation

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  34. app/src/main/kotlin/clean/news/app/

    ├── item

    │ ├── GetChildren

    │ ├── GetItemById

    │ ├── GetItemsByListType

    │ └── SaveItem

    └── user

    ├── GetUserById

    └── SaveUser

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  35. app/src/main/kotlin/clean/news/app/

    ├── item

    │ ├── GetChildren

    │ ├── GetItemById

    │ ├── GetItemsByListType

    │ └── SaveItem

    └── user

    ├── GetUserById

    └── SaveUser

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  36. Entities

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  37. “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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  38. apply plugin: 'java'


    dependencies {

    }
    Core

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  39. core/src/main/kotlin/clean/news/core/entity/

    ├── Item.kt

    └── User.kt

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  40. 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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  41. 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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  42. 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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  43. Entities
    • Contain enterprise wide business rules
    • Encapsulate high-level rules
    • Unaffected by external layers

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  44. Use Cases

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  45. “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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  46. 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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  47. 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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  48. apply plugin: 'java'


    dependencies {

    compile project(':core')

    }
    Core
    App

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  49. 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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  50. Presenter
    Controller
    Use Case
    Input Port
    Use Case
    Interactor
    Use Case
    Output Port
    Flow of Control

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  51. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  52. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  53. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  54. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  55. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  56. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  57. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  58. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  59. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  60. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  61. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  62. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  63. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  64. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  65. Request Model
    Response Model
    Use Case Boundary
    Boundary
    Presentation Model

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  66. interface UseCase {


    fun execute(request: I): Observable


    interface Request


    interface Response


    }

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  67. interface UseCase {


    fun execute(request: I): Observable


    interface Request


    interface Response


    }

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  68. interface UseCase {


    fun execute(request: I): Observable


    interface Request


    interface Response


    }

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  69. interface UseCase {


    fun execute(request: I): Observable


    interface Request


    interface Response


    }

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  70. interface UseCase {


    fun execute(request: I): Observable


    interface Request


    interface Response


    }

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  71. interface UseCase {


    fun execute(request: I): Observable


    interface Request


    interface Response


    }

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  72. interface UseCase {


    fun execute(request: I): Observable


    interface Request


    interface Response


    }

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  73. interface UseCase {


    fun execute(request: I): Observable


    interface Request


    interface Response


    }

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  74. interface UseCase {.


    fun execute(): Observable


    }.

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  75. interface UseCase1 {.


    fun execute(arg1: A): Observable


    }.

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  76. interface UseCase2 {.


    fun execute(arg1: A, arg2: B): Observable


    }.

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  77. interface UseCase3 {.


    fun execute(arg1: A, arg2: B, arg3: C): Observable


    }.

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  78. 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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  79. GetChildren.Request
    GetChildren.Response
    GetChildren ItemNetworkDataSource
    ItemRetrofitDataSource
    ItemDetailsViewModel

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  80. GetChildren.Request
    GetChildren.Response
    GetChildren ItemNetworkDataSource
    ItemRetrofitDataSource
    ItemDetailsViewModel

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  81. GetChildren.Request
    GetChildren.Response
    GetChildren ItemNetworkDataSource
    ItemRetrofitDataSource
    ItemDetailsViewModel

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  82. GetChildren.Request
    GetChildren.Response
    GetChildren ItemNetworkDataSource
    ItemRetrofitDataSource
    ItemDetailsViewModel

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  83. GetChildren.Request
    GetChildren.Response
    GetChildren ItemNetworkDataSource
    ItemRetrofitDataSource
    ItemDetailsViewModel

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  84. GetChildren.Request
    GetChildren.Response
    GetChildren ItemNetworkDataSource
    ItemRetrofitDataSource
    ItemDetailsViewModel

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  85. GetChildren.Request
    GetChildren.Response
    GetChildren ItemNetworkDataSource
    ItemRetrofitDataSource
    ItemDetailsViewModel

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  86. 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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  87. 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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  88. 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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  89. 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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  90. 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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  91. 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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  92. 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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  93. 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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  94. interface DataSource {

    fun getAll(): Observable>


    fun getById(id: ID): Observable


    fun save(t: T): Observable

    }

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  95. interface ItemDataSource : DataSource {

    fun getItems(listType: ListType): Observable>


    fun getChildren(item: Item): Observable>

    }

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  96. interface ItemDiskDataSource : ItemDataSource
    interface ItemMemoryDataSource : ItemDataSource
    interface ItemNetworkDataSource : ItemDataSource

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  97. 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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  98. Interface Adapters

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

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  100. apply plugin: 'java'


    dependencies {

    compile project(':app')

    }
    Core
    App
    Presentation
    Data

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  101. ItemNetworkDataSource
    GetChildren
    ItemRetrofitDataSource
    ItemDetailViewModel

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  102. ItemNetworkDataSource
    GetChildren
    ItemRetrofitDataSource
    ItemDetailViewModel

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  103. ItemNetworkDataSource
    GetChildren
    ItemRetrofitDataSource
    ItemDetailViewModel

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  104. ItemNetworkDataSource
    GetChildren
    ItemRetrofitDataSource
    ItemDetailViewModel

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  105. ItemNetworkDataSource
    GetChildren
    ItemRetrofitDataSource
    ItemDetailViewModel

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  106. presentation/src/main/kotlin/clean/news/presentation/model/

    ├── Model.kt

    ├── item

    │ ├── ItemDetailViewModel.kt

    │ ├── ItemListViewModel.kt

    │ └── ItemUrlViewModel.kt

    └── main

    └── MainViewModel.kt

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  107. 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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  108. 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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  109. 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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  110. 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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  111. class ItemRetrofitDataSource @Inject constructor(

    private val itemService: ItemService) : ItemNetworkDataSource {


    override fun getById(id: Long): Observable {

    return itemService.getById(id)

    }

    }

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  112. class ItemRetrofitDataSource @Inject constructor(

    private val itemService: ItemService) : ItemNetworkDataSource {


    override fun getById(id: Long): Observable {

    return itemService.getById(id)

    }

    }

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  113. class ItemRetrofitDataSource @Inject constructor(

    private val itemService: ItemService) : ItemNetworkDataSource {


    override fun getById(id: Long): Observable {

    return itemService.getById(id)

    }

    }

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  114. interface ItemService {

    @GET("item/{item_id}.json")

    fun getById(@Path("item_id") id: Long): Observable

    }

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  115. class ItemRetrofitDataSource @Inject constructor(

    private val itemService: ItemService) : ItemNetworkDataSource {


    override fun getById(id: Long): Observable {

    return itemService.getById(id)

    }

    }

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

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  117. Frameworks and Drivers

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

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  119. apply plugin: 'com.android.application'


    dependencies {

    compile project(':presentation')

    compile project(':data')

    }
    Core
    App
    Presentation
    Data
    Android
    Desktop

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  120. class ItemDetailView : RelativeLayout {

    @Inject

    lateinit var model: ItemDetailViewModel


    @JvmOverloads

    constructor(...) : super(context, attrs, defStyle) {

    ComponentService.getService(context)?.inject(this)

    }
    }

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  121. class ItemDetailView : RelativeLayout {

    @Inject

    lateinit var model: ItemDetailViewModel


    @JvmOverloads

    constructor(...) : super(context, attrs, defStyle) {

    ComponentService.getService(context)?.inject(this)

    }
    }

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  122. class ItemDetailView : RelativeLayout {

    @Inject

    lateinit var model: ItemDetailViewModel


    @JvmOverloads

    constructor(...) : super(context, attrs, defStyle) {

    ComponentService.getService(context)?.inject(this)

    }
    }

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  123. @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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  124. @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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  125. @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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  126. 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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  127. 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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  128. Frameworks and Drivers
    • Glue code to communicate inwards
    • Delivery mechanism
    • Dependency providers

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  129. POLICIES
    MECHANISMS

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  130. 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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  131. Questions?
    @pardom
    michaelpardo.com

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