Reactive Workflows

Our MVP app is too big. Introducing the Workflow pattern to try to get it back under control. Plays well with Rx, minimizes platform-specific dependencies. Woo hoo!

https://droidcon-server.herokuapp.com/showSession/103028
https://www.youtube.com/watch?v=KjoMnsc2lPo

Transcript

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2. reacting to code sprawl
   Reactive
   Workflows
   Ray Ryan
   

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3. Key-based MVP
   the legacy
   

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4. Key-based MVP
   Key
   flow.set(Key)
   

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5. Key-based MVP
   Key
   View
   

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6. Key-based MVP
   Key
   Presenter
   View
   

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7. Key-based MVP
   Key
   Presenter
   View
   Model Model Model
   

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8. Key-based MVP
   CartScreen
   Cart
   Presenter
   CartView
   Item
   Library
   Cart
   

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9. Key-based MVP
   CartScreen
   Cart
   Presenter
   CartView
   Item
   Library
   Cart
   flow.set(ChargeScreen)
   

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10. ChargeScreen
    Key-based MVP
    CartScreen
    Cart
    Presenter
    CartView
    Item
    Library
    Cart
    

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11. Key-based MVP
    ChargeScreen
    CartScreen
    

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12. Key-based MVP
    Charge
    Presenter
    Charge
    View
    Cart Bill
    Card
    Reader
    ChargeScreen
    CartScreen
    

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13. Key-based MVP
    Charge
    Presenter
    Charge
    View
    Cart Bill
    Card
    Reader
    ChargeScreen
    CartScreen
    

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14. Key-based MVP
    Charge
    Presenter
    Charge
    View
    Cart Bill
    Card
    Reader
    ChargeScreen
    CartScreen
    

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15. Nav logic sprawl
    ChargeScreen
    CartScreen
    

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16. Nav logic sprawl
    ChargeScreen
    CartScreen TipScreen
    

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17. Nav logic sprawl
    ChargeScreen
    CartScreen TipScreen
    SignatureScreen
    

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18. Nav logic sprawl
    ChargeScreen
    CartScreen TipScreen
    SignatureScreen
    

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19. Nav logic sprawl
    ChargeScreen
    CartScreen TipScreen
    SignatureScreen
    ReceiptScreen
    

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20. Nav logic sprawl
    ChargeScreen
    CartScreen TipScreen
    SignatureScreen
    ReceiptScreen
    

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21. Nav logic sprawl
    ChargeScreen
    CartScreen TipScreen
    SignatureScreen
    ReceiptScreen
    

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22. Nav logic sprawl
    ChargeScreen
    CartScreen TipScreen
    SignatureScreen
    ReceiptScreen
    

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23. Nav logic sprawl
    ChargeScreen
    CartScreen TipScreen
    SignatureScreen
    ReceiptScreen
    Payment
    Runner
    

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24. Nav logic sprawl
    ChargeScreen
    CartScreen TipScreen
    SignatureScreen
    ReceiptScreen
    Payment
    Runner
    SettingsScreen
    

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25. Nav & biz logic entangled
    Charge
    Presenter
    Bill
    Card
    Reader
    ChargeScreen
    Payment
    Runner
    

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26. Nav & biz logic entangled
    Charge
    Presenter
    Bill
    Card
    Reader
    ChargeScreen
    Payment
    Runner
    cardSwiped()
    

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27. Nav & biz logic entangled
    Charge
    Presenter
    Bill
    Card
    Reader
    ChargeScreen
    Payment
    Runner
    setCardInfo()
    cardSwiped()
    

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28. Nav & biz logic entangled
    Charge
    Presenter
    Bill
    Card
    Reader
    ChargeScreen
    Payment
    Runner
    setCardInfo()
    cardSwiped()
    next()
    

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29. Nav & biz logic entangled
    Charge
    Presenter
    Bill
    Card
    Reader
    ChargeScreen
    Payment
    Runner
    setCardInfo()
    cardSwiped()
    show tip screen?
    next()
    

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30. show signature screen?
    Nav & biz logic entangled
    Charge
    Presenter
    Bill
    Card
    Reader
    ChargeScreen
    Payment
    Runner
    setCardInfo()
    cardSwiped()
    show tip screen?
    next()
    

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31. show signature screen?
    Nav & biz logic entangled
    Charge
    Presenter
    Bill
    Card
    Reader
    ChargeScreen
    Payment
    Runner
    setCardInfo()
    finishPayment()
    cardSwiped()
    show tip screen?
    next()
    

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32. show signature screen?
    Nav & biz logic entangled
    Charge
    Presenter
    Bill
    Card
    Reader
    ChargeScreen
    Payment
    Runner
    setCardInfo()
    finishPayment()
    cardSwiped()
    show tip screen?
    next()
    

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33. AddCustomer
    Runner
    Awkward reuse
    Cart
    Presenter
    CartScreen
    Cart
    

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34. AddCustomer
    Runner
    Awkward reuse
    Cart
    Presenter
    start()
    CartScreen
    Cart
    

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35. PickCustomerScreen
    AddCustomer
    Runner
    Awkward reuse
    Cart
    Presenter
    start()
    CartScreen
    Cart
    

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36. AddCustomer
    Runner
    Awkward reuse
    Pick
    Customer
    Presenter
    PickCustomerScreen
    CartScreen
    Cart
    

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37. AddCustomer
    Runner
    Awkward reuse
    Pick
    Customer
    Presenter
    PickCustomerScreen
    CartScreen
    Cart
    setCustomer()
    + Customer
    

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38. AddCustomer
    Runner
    Awkward reuse
    Receipt
    Presenter
    ReceiptScreen
    Receipt
    

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39. AddCustomer
    Runner
    Awkward reuse
    Receipt
    Presenter
    start()
    ReceiptScreen
    Receipt
    flow.set(PickCustomerScreen)
    

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40. AddCustomer
    Runner
    Awkward reuse
    Receipt
    Presenter
    start()
    ReceiptScreen
    Receipt
    PickCustomerScreen
    

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41. AddCustomer
    Runner
    Awkward reuse
    Pick
    Customer
    Presenter
    PickCustomerScreen
    ReceiptScreen
    

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42. AddCustomer
    Runner
    Awkward reuse
    Pick
    Customer
    Presenter
    PickCustomerScreen
    ReceiptScreen
    Cart Receipt
    ?
    

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43. AddCustomer
    Runner
    Awkward reuse
    Pick
    Customer
    Presenter
    PickCustomerScreen
    ReceiptScreen
    ?
    + Customer
    

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44. AddCustomer
    Runner
    Awkward reuse
    Pick
    Customer
    Presenter
    PickCustomerScreen
    ReceiptScreen
    ? + Customer
    

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45. Still, pretty good enough
    Nearly two hundred contributors
    Around three hundred screens
    Ships every two weeks
    

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46. Good enough don’t scale
    four years later
    

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47. Good enough don’t scale
    12 minute clean build
    2-4 minute rebuild
    Spaghetti of the commons
    

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48. iOS even worse
    ViewControllers full of business logic
    WWAD syndrome
    • Static singletons
    • CoreData all the things
    • Undiffable XIB, Storyboard files
    

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49. Learned helplessness
    Each platform > 750,000 LOC
    Remember, THREE HUNDRED SCREENS
    Nearly half just in payment flow
    Grassroots heroics no longer practical
    

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50. Learned helplessness
    Each platform > 750,000 LOC
    Remember, THREE HUNDRED SCREENS
    Nearly half just in payment flow
    Grassroots heroics no longer practical
    

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51. Reclaiming the commons
    we bring glad tidings from the future
    

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52. Reclaiming the commons
    Make fixing things someone’s job
    Make success possible
    • Define the problems
    • Describe utopia
    • Declare and execute two year plan
    Define the problems
    

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53. Define the problems
    Edit, compile, debug loop is too slow
    The code is too complex
    Dependencies are too interconnected
    

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54. Define the problems
    Edit, compile, debug loop is too slow
    The code is too complex
    Dependencies are too interconnected
    Modularize: small code blocks build faster
    Modularize: big features from simpler parts
    Modularize: dependencies are a DAG
    

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55. Describe Utopia
    

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56. Describe Utopia
    

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57. Utopia's core principals
    Immutability is assumed
    Be reactive: push, don’t pull
    Natural separation of UI and business concerns
    Uniformity of API across platforms
    Uniformity
    Utopia
    

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58. “Uniformity?” Code sharing?
    Maybe
    Writing is the easy part, maintenance is forever
    Shared code is foreign code
    Have you considered…
    • Shared tests
    • Shared API definitions (protocol buffers)
    Uniformity
    

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59. “Uniformity?” Code sharing?
    Maybe
    Writing is the easy part, maintenance is forever
    Shared code is foreign code
    Have you considered…
    • Shared tests
    • Shared API definitions (protocol buffers)
    Uniformity
    

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60. Workflows and Bricks
    Brick
    

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61. Workflows and Bricks
    Bricks
    Business model
    i/o
    Brick
    

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62. Workflows and Bricks
    Bricks
    Workflows
    Business model
    i/o
    App logic
    UI modeling
    Brick
    

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63. Workflows and Bricks
    Bricks
    Workflows
    Container
    Business model
    i/o
    App logic
    UI modeling
    Rendering
    UI event handling
    View
    Factory
    Brick
    

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64. Workflows and Bricks
    Bricks
    Workflows
    Container
    Business model
    i/o
    App logic
    UI modeling
    Rendering
    UI event handling
    Platform
    neutral*
    View code
    View
    Factory
    Brick
    

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65. “Brick” rhymes with “schmego”
    Brick
    

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66. “Brick” rhymes with “schmego”
    

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67. “Brick” rhymes with “schmego”
    

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68. “Brick” rhymes with “schmego”
    setFoo(FooValue f) Observable bar();
    

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69. “Brick” rhymes with “schmego”
    setFoo(FooValue f) Observable bar();
    

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70. “Brick” rhymes with “schmego”
    BarValue getBar();
    setFoo(FooValue f) Observable bar();
    

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71. “Brick” rhymes with “schmego”
    BarValue getBar();
    setFoo(FooValue f) Observable bar();
    

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72. “Brick” rhymes with “schmego”
    BarValue getBar();
    setFoo(FooValue f) Observable bar();
    SqlBrite / SqlDelight
    *RxPreferences, *Rooms
    Retrofit
    

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73. Build big bricks from small bricks
    

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74. Build big bricks from small bricks
    

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75. Build big bricks from small bricks
    

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76. Build big bricks from small bricks
    j2Objc JavaScript
    

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77. enum class StateOfPlay {
    PLAYING, VICTORY, DRAW
    }
    

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78. enum class StateOfPlay {
    PLAYING, VICTORY, DRAW
    }
    enum class MARK {
    EMPTY, X, O
    }
    

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79. enum class StateOfPlay {
    PLAYING, VICTORY, DRAW
    }
    enum class MARK {
    EMPTY, X, O
    }
    data class Player(
    val id: String,
    val name: String
    )
    

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80. data class GameState(
    val id: String,
    val playerX: Player,
    val playerO: Player,
    val stateOfPlay: StateOfPlay,
    val grid: List>,
    val activePlayerId: String
    )
    enum class StateOfPlay {
    PLAYING, VICTORY, DRAW
    }
    enum class MARK {
    EMPTY, X, O
    }
    data class Player(
    val id: String,
    val name: String
    )
    

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81. class GameRunner {
    fun newGame(xPlayerName: String, oPlayerName: String) {}
    fun restoreGame(clientId: String) {}
    fun takeSquare(row: Int, col: Int) {}
    fun end() {}
    fun gameState(): Observable {}
    }
    

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82. class GameRunner {
    /** @throws AssertionError if not called from main thread */
    fun newGame(xPlayerName: String, oPlayerName: String) {}
    /** @throws AssertionError if not called from main thread */
    fun restoreGame(clientId: String) {}
    /** @throws AssertionError if not called from main thread */
    fun takeSquare(row: Int, col: Int) {}
    /** @throws AssertionError if not called from main thread */
    fun end() {}
    fun gameState(): Observable {}
    }
    fun newGame(xPlayerName: String, oPlayerName: String)
    fun restoreGame(clientId: String)
    class GameRunner {
    

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83. class GameRunner {
    /** @throws AssertionError if not called from main thread */
    fun newGame(xPlayerName: String, oPlayerName: String) {}
    /** @throws AssertionError if not called from main thread */
    fun restoreGame(clientId: String) {}
    /** @throws AssertionError if not called from main thread */
    fun takeSquare(row: Int, col: Int) {}
    /** @throws AssertionError if not called from main thread */
    fun end() {}
    fun gameState(): Observable {}
    }
    fun newGame(xPlayerName: String, oPlayerName: String)
    fun restoreGame(clientId: String)
    class GameRunner {
    observeOn(mainThread())
    speakerdeck.com/rjrjr/
    where-the-reactive-rubber-meets-the-road
    

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84. class GameRunner {
    /** @throws AssertionError if not called from main thread */
    fun newGame(xPlayerName: String, oPlayerName: String) {}
    /** @throws AssertionError if not called from main thread */
    fun restoreGame(clientId: String) {}
    /** @throws AssertionError if not called from main thread */
    fun takeSquare(row: Int, col: Int) {}
    /** @throws AssertionError if not called from main thread */
    fun end() {}
    fun gameState(): Observable {}
    }
    fun newGame(xPlayerName: String, oPlayerName: String)
    fun restoreGame(clientId: String)
    class GameRunner {
    

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85. class GameRunner {
    

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86. class GameRunner {
    sealed class Command {
    data class NewGame(val xPlayer: String, val yPlayer: String): Command()
    data class RestoreGame(val id: String): Command()
    data class TakeSquare(val row: Int, val col: Int): Command()
    object End: Command()
    }
    fun asTransformer():
    Observable.Transformer {
    }
    }
    

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87. class GameRunner {
    sealed class Command {
    data class NewGame(val xPlayer: String, val yPlayer: String): Command()
    data class RestoreGame(val id: String): Command()
    data class TakeSquare(val row: Int, val col: Int): Command()
    object End: Command()
    }
    fun asTransformer():
    Observable.Transformer {
    }
    }
    search for:
    Dan Lew transformer
    

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88. Workflow through the brickyard
    

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89. Remember these things?
    Charge
    Presenter
    Bill
    ChargeScreen
    Payment
    Runner
    setCardInfo()
    finishPayment()
    next()
    flow.set(TipScreen)
    Charge
    View
    

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90. Remember these things?
    Charge
    Presenter
    Bill
    ChargeScreen
    Payment
    Runner
    setCardInfo()
    finishPayment()
    next()
    flow.set(TipScreen)
    Charge
    View
    

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91. Remember these things?
    Charge
    Presenter
    Bill
    ChargeScreen
    Payment
    Runner
    setCardInfo()
    finishPayment()
    next()
    flow.set(TipScreen)
    Charge
    View
    

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92. Remember these things?
    Charge
    Presenter
    Bill
    ChargeScreen
    Payment
    Runner
    setCardInfo()
    finishPayment()
    next()
    flow.set(TipScreen)
    Charge
    View
    

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93. Presenter
    Runner + = Workflow
    

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94. Workflow as
    Presenter
    + = Workflow
    start(I input) Maybe result()
    abort()
    pipeline
    

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95. Workflow as
    = Workflow
    start(I input) Maybe result()
    abort()
    ui driver
    Observable screen()
    

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96. Rhymes with “view model”
    /** Allows interaction with a [Workflow] in a particular state. */
    abstract class WorkflowScreen protected constructor(
    /** Uniquely identifies this screen. */
    val key: String,
    /** Stream of data to render this screen. */
    val screenData: Observable,
    /** Callback methods (click handlers, etc.) handled by this screen. */
    val eventHandler: E
    )
    

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97. LoginScreen AuthorizingScreen SecondFactorScreen
    

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98. class LoginScreen(
    errorMessage: Observable,
    eventHandler: Events
    ) : WorkflowScreen(KEY, errorMessage, eventSink) {
    companion object {
    val KEY = LoginScreen::class.name
    }
    interface Events {
    fun onLogin(event: SubmitLogin)
    }
    data class SubmitLogin(
    val email: String,
    val password: String
    )
    }
    

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99. class LoginScreen(
    errorMessage: Observable,
    eventHandler: Events
    ) : WorkflowScreen(KEY, errorMessage, eventSink) {
    companion object {
    val KEY = LoginScreen::class.name
    }
    interface Events {
    fun onLogin(event: SubmitLogin)
    }
    data class SubmitLogin(
    val email: String,
    val password: String
    )
    }
    

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100. class LoginScreen(
     errorMessage: Observable,
     eventHandler: Events
     ) : WorkflowScreen(KEY, errorMessage, eventSink) {
     companion object {
     val KEY = LoginScreen::class.name
     }
     interface Events {
     fun onLogin(event: SubmitLogin)
     }
     data class SubmitLogin(
     val email: String,
     val password: String
     )
     }
     

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101. class LoginScreen(
     errorMessage: Observable,
     eventHandler: Events
     ) : WorkflowScreen(KEY, errorMessage, eventSink) {
     companion object {
     val KEY = LoginScreen::class.name
     }
     interface Events {
     fun onLogin(event: SubmitLogin)
     }
     data class SubmitLogin(
     val email: String,
     val password: String
     )
     }
     

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102. class ConfirmChargeCardOnFileScreen(
     screenData: Observable,
     eventHandler: Events
     ) : WorkflowScreen(KEY, screenData, eventHandler) {
     companion object {
     val KEY = ConfirmChargeCardOnFileScreen::class.name
     }
     data class ScreenData(
     val amountDue: Money,
     val customerName: String,
     val cardNameAndNumber: String,
     val instrumentIndex: Int)
     interface Events {
     fun doNotChargeCardOnFile()
     fun chargeCardOnFile(tenderedAmount: Money, instrumentIndex: Int)
     }
     

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103. Workflow as
     = Workflow
     start(I input) Maybe result()
     abort()
     view model source
     Observable screen()
     

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104. Workflow as
     = Workflow
     start(I input) Maybe result()
     abort()
     view model source
     Observable screen() ✔
     

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105. View
     Factory
     Container
     Workflow as
     = Workflow
     start(I input) Maybe result()
     abort()
     view model source
     Observable screen()
     RootView
     ✔
     

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106. class AuthViewFactory : AbstractViewFactory(asList(
     bindLayout(LoginScreen.KEY, R.layout.login) { screen ->
     LoginCoordinator(screen as LoginScreen)
     },
     bindLayout(AuthorizingScreen.KEY, R.layout.authorizing) { screen ->
     AuthorizingCoordinator(screen as AuthorizingScreen)
     },
     bindLayout(SecondFactorScreen.KEY, R.layout.second_factor) { screen ->
     SecondFactorCoordinator(screen as SecondFactorScreen)
     }
     ))
     

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107. class LoginCoordinator(private val screen: LoginScreen) : Coordinator() {
     private var subscription: Subscription = Subscriptions.unsubscribed()
     override fun attach(view: View) {
     

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108. class LoginCoordinator(private val screen: LoginScreen) : Coordinator() {
     private var subscription: Subscription = Subscriptions.unsubscribed()
     override fun attach(view: View) {
     val error = view.findViewById(R.id.login_error_message) as TextView
     val email = view.findViewById(R.id.login_email) as EditText
     val password = view.findViewById(R.id.login_password) as EditText
     val button = view.findViewById(R.id.login_button) as Button
     

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109. class LoginCoordinator(private val screen: LoginScreen) : Coordinator() {
     private var subscription: Subscription = Subscriptions.unsubscribed()
     override fun attach(view: View) {
     val error = view.findViewById(R.id.login_error_message) as TextView
     val email = view.findViewById(R.id.login_email) as EditText
     val password = view.findViewById(R.id.login_password) as EditText
     val button = view.findViewById(R.id.login_button) as Button
     button.setOnClickListener { _ ->
     val event = SubmitLogin(email.text.toString(),
     password.text.toString())
     screen.eventHandler.login(event)
     }
     

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110. class LoginCoordinator(private val screen: LoginScreen) : Coordinator() {
     private var subscription: Subscription = Subscriptions.unsubscribed()
     override fun attach(view: View) {
     val error = view.findViewById(R.id.login_error_message) as TextView
     val email = view.findViewById(R.id.login_email) as EditText
     val password = view.findViewById(R.id.login_password) as EditText
     val button = view.findViewById(R.id.login_button) as Button
     button.setOnClickListener { _ ->
     val event = SubmitLogin(email.text.toString(),
     password.text.toString())
     screen.eventHandler.login(event)
     }
     subscription = screen.screenData.subscribe { error.text = it }
     }
     

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111. class LoginCoordinator(private val screen: LoginScreen) : Coordinator() {
     private var subscription: Subscription = Subscriptions.unsubscribed()
     override fun attach(view: View) {
     …
     }
     override fun detach(view: View?) {
     subscription.unsubscribe()
     }
     

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112. class LoginCoordinator(private val screen: LoginScreen) : Coordinator() {
     private var subscription: Subscription = Subscriptions.unsubscribed()
     override fun attach(view: View) {
     …
     }
     override fun detach(view: View?) {
     subscription.unsubscribe()
     }
     search for:
     square coordinators
     

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113. Workflow as
     = Workflow
     start(I input) Maybe result()
     abort()
     state machine
     Container
     Observable screen()
     View
     Factory
     RootView
     ✔
     

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114. Workflow as
     = Workflow
     start(I input) Maybe result()
     abort()
     state machine
     Container
     Observable screen()
     View
     Factory
     RootView
     ✔
     ✔
     + Square Coordinators
     

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115. Workflow as
     = Workflow
     start(I input) Maybe result()
     abort()
     state machine
     Container
     Observable screen()
     View
     Factory
     RootView
     ✔
     ✔
     + Square Coordinators
     

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116. class AuthWorkflow(): Workflow
     

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117. class AuthWorkflow(): Workflow,
     LoginScreen.Events, SecondFactorScreen.Events
     

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118. class AuthWorkflow(): Workflow,
     LoginScreen.Events, SecondFactorScreen.Events {
     private val currentScreen = BehaviorSubject.create()
     

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119. class AuthWorkflow(): Workflow,
     LoginScreen.Events, SecondFactorScreen.Events {
     private val currentScreen = BehaviorSubject.create()
     private val loginMessage = BehaviorSubject.create("")
     private val authorizingMessage = BehaviorSubject.create()
     private val secondFactorMessage = BehaviorSubject.create()
     

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120. class AuthWorkflow(): Workflow,
     LoginScreen.Events, SecondFactorScreen.Events {
     private val currentScreen = BehaviorSubject.create()
     private val loginMessage = BehaviorSubject.create("")
     private val authorizingMessage = BehaviorSubject.create()
     private val secondFactorMessage = BehaviorSubject.create()
     override fun screen(): Observable =
     currentScreen.map { it ->
     when (it) {
     LoginScreen.KEY -> LoginScreen(loginMessage, this)
     AuthorizingScreen.KEY -> AuthorizingScreen(authorizingMessage)
     SecondFactorScreen.KEY -> SecondFactorScreen(secondFactorMessage, this)
     else -> throw IllegalArgumentException("Unknown key " + it)
     }
     }
     

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121. class AuthWorkflow(): Workflow,
     LoginScreen.Events, SecondFactorScreen.Events {
     …
     

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122. class AuthWorkflow(): Workflow,
     LoginScreen.Events, SecondFactorScreen.Events {
     …
     override fun onLogin(event: LoginScreen.SubmitLogin) {
     stateMachine.onEvent(event)
     }
     override fun onSecondFactor(event: SecondFactorScreen.SecondFactor) {
     stateMachine.onEvent(event)
     }
     

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123. internal enum class State {
     LOGIN_PROMPT, AUTHORIZING, SECOND_FACTOR_PROMPT, DONE
     }
     

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124. internal enum class State {
     LOGIN_PROMPT, AUTHORIZING, SECOND_FACTOR_PROMPT, DONE
     }
     init {
     stateMachine = FiniteStateMachine(
     onEntry(AUTHORIZING) { currentScreen.onNext(AuthorizingScreen.KEY) },
     onEntry(SECOND_FACTOR_PROMPT) {
     currentScreen.onNext(SecondFactorScreen.KEY)
     },
     

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125. internal enum class State {
     LOGIN_PROMPT, AUTHORIZING, SECOND_FACTOR_PROMPT, DONE
     }
     init {
     stateMachine = FiniteStateMachine(
     …
     

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126. internal enum class State {
     LOGIN_PROMPT, AUTHORIZING, SECOND_FACTOR_PROMPT, DONE
     }
     init {
     stateMachine = FiniteStateMachine(
     …
     transition(LOGIN_PROMPT, SubmitLogin::class, AUTHORIZING)
     .doAction { doLogin(it) },
     transition(AUTHORIZING, AuthResponse::class, LOGIN_PROMPT)
     .onlyIf { isLoginFailure(it) }
     .doAction { response ->
     val errorMessage = response.errorMessage
     loginMessage.onNext(errorMessage)
     },
     

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127. internal enum class State {
     LOGIN_PROMPT, AUTHORIZING, SECOND_FACTOR_PROMPT, DONE
     }
     init {
     stateMachine = FiniteStateMachine(
     …
     transition(LOGIN_PROMPT, SubmitLogin::class, AUTHORIZING)
     .doAction { doLogin(it) },
     transition(AUTHORIZING, AuthResponse::class, LOGIN_PROMPT)
     .onlyIf { isLoginFailure(it) }
     .doAction { response ->
     val errorMessage = response.errorMessage
     loginMessage.onNext(errorMessage)
     },
     search for:
     Andy Matuschak states
     

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128. NewGameScreen GamePlayScreen GameOverScreen
     ConfirmQuitScreen
     

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129. class TicTacToeViewFactory private constructor()
     : AbstractViewFactory(asList(
     bindLayout(NewGameScreen.KEY, layout.new_game_layout
     ) { screen -> NewGameCoordinator(screen as NewGameScreen) },
     bindLayout(GamePlayScreen.KEY, layout.game_play_layout
     ) { screen -> GamePlayCoordinator(screen as GamePlayScreen) },
     bindLayout(GameOverScreen.KEY, layout.game_play_layout
     ) { screen -> GameOverCoordinator(screen as GameOverScreen) },
     bindDialog(ConfirmQuitScreen.KEY
     ) { screen -> ConfirmQuitDialogFactory(screen as ConfirmQuitScreen) }
     ))
     

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130. class TicTacToeViewFactory private constructor()
     : AbstractViewFactory(asList(
     bindLayout(NewGameScreen.KEY, layout.new_game_layout
     ) { screen -> NewGameCoordinator(screen as NewGameScreen) },
     bindLayout(GamePlayScreen.KEY, layout.game_play_layout
     ) { screen -> GamePlayCoordinator(screen as GamePlayScreen) },
     bindLayout(GameOverScreen.KEY, layout.game_play_layout
     ) { screen -> GameOverCoordinator(screen as GameOverScreen) },
     bindDialog(ConfirmQuitScreen.KEY
     ) { screen -> ConfirmQuitDialogFactory(screen as ConfirmQuitScreen) }
     ))
     

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131. class TicTacToeViewFactory private constructor()
     : AbstractViewFactory(asList(
     bindLayout(NewGameScreen.KEY, layout.new_game_layout
     ) { screen -> NewGameCoordinator(screen as NewGameScreen) },
     bindLayout(GamePlayScreen.KEY, layout.game_play_layout
     ) { screen -> GamePlayCoordinator(screen as GamePlayScreen) },
     bindLayout(GameOverScreen.KEY, layout.game_play_layout
     ) { screen -> GameOverCoordinator(screen as GameOverScreen) },
     bindDialog(ConfirmQuitScreen.KEY
     ) { screen -> ConfirmQuitDialogFactory(screen as ConfirmQuitScreen) }
     ))
     

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132. class TicTacToeWorkflow(
     private val gameRunner: GameRunner
     ): Workflow
     

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133. class TicTacToeWorkflow(
     private val gameRunner: GameRunner
     ): Workflow,
     NewGameScreen.Events, GamePlayScreen.Events,
     ConfirmQuitScreen.Events, GameOverScreen.Events {
     

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134. class TicTacToeWorkflow(
     private val gameRunner: GameRunner
     ): Workflow,
     NewGameScreen.Events, GamePlayScreen.Events,
     ConfirmQuitScreen.Events, GameOverScreen.Events {
     private val gameStates: Observable =
     gameRunner.gameState().startWith(NO_GAME)
     

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135. class TicTacToeWorkflow(
     private val gameRunner: GameRunner
     ): Workflow,
     NewGameScreen.Events, GamePlayScreen.Events,
     ConfirmQuitScreen.Events, GameOverScreen.Events {
     private val gameStates: Observable =
     gameRunner.gameState().startWith(NO_GAME)
     companion object {
     private val FAKE_ID = UUID.randomUUID().toString()
     private val NO_GAME = TicTacToeGameState.newGame(FAKE_ID,
     Player(FAKE_ID, "X"), Player(FAKE_ID, "O"))
     }
     

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136. class TicTacToeWorkflow(
     private val gameRunner: GameRunner
     ): Workflow,
     NewGameScreen.Events, GamePlayScreen.Events,
     ConfirmQuitScreen.Events, GameOverScreen.Events {
     private val gameStates: Observable =
     gameRunner.gameState().startWith(NO_GAME)
     …
     

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137. class TicTacToeWorkflow(
     private val gameRunner: GameRunner
     ): Workflow,
     NewGameScreen.Events, GamePlayScreen.Events,
     ConfirmQuitScreen.Events, GameOverScreen.Events {
     private val gameStates: Observable =
     gameRunner.gameState().startWith(NO_GAME)
     private val quitting = BehaviorSubject.create(false)
     …
     

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138. class TicTacToeWorkflow(
     private val gameRunner: GameRunner
     ): Workflow,
     NewGameScreen.Events, GamePlayScreen.Events,
     ConfirmQuitScreen.Events, GameOverScreen.Events {
     private val gameStates: Observable =
     gameRunner.gameState().startWith(NO_GAME)
     private val quitting = BehaviorSubject.create(false)
     private val screen = combineLatest(gameStates, quitting,
     { gameState, quitting -> update(gameState, quitting) })
     .replay(1)
     override fun screen(): Observable> = screen
     …
     

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139. class TicTacToeWorkflow(
     private val gameRunner: GameRunner
     ): Workflow,
     NewGameScreen.Events, GamePlayScreen.Events,
     ConfirmQuitScreen.Events, GameOverScreen.Events {
     …
     

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140. class TicTacToeWorkflow(
     private val gameRunner: GameRunner
     ): Workflow,
     NewGameScreen.Events, GamePlayScreen.Events,
     ConfirmQuitScreen.Events, GameOverScreen.Events {
     …
     private fun update(gameState: GameState, quitting: Boolean):
     WorkflowScreen<*,*> {
     if (quitting) return ConfirmQuitScreen(this)
     if (gameState == NO_GAME) NewGameScreen(this)
     return when (gameState.stateOfPlay) {
     PLAYING -> GamePlayScreen(gameStates, this)
     VICTORY, DRAW -> GameOverScreen(gameStates, this)
     }
     }
     …
     

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141. RootView
     View
     Factory
     Container
     Workflow
     

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142. RootView
     View
     Factory
     Container
     Workflow
     

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143. RootView
     Key
     ScreenData
     Events
     WorkflowScreen
     View
     Factory
     Container
     Workflow
     

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144. RootView
     Key
     ScreenData
     Events
     WorkflowScreen
     View
     Factory
     Container
     Workflow
     

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145. RootView
     Key
     ScreenData
     Events
     WorkflowScreen
     View
     Factory
     Container
     Workflow
     

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146. RootView
     View
     Factory
     Container
     Workflow
     

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147. RootView
     Key
     ScreenData
     Events
     WorkflowScreen
     View
     Factory
     Container
     Workflow
     

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148. RootView
     View
     Factory
     Container
     Workflow
     

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149. Workflow
     You said these things compose
     

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150. Workflow
     You said these things compose
     Auth
     Workflow
     Game
     Workflow
     

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151. new CompositeWorkflow<>(
     // Start in the AuthWorkflow. When it finishes, kick off
     // a TicTacToe game.
     new WorkflowBinding<>(AuthWorkflow.class,
     () -> ignoreStartArg(authWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT))),
     // When a TicTacToe game ends, start another one.
     new WorkflowBinding<>(TicTacToeWorkflow.class,
     () -> ignoreStartArg(ticTacToeWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT)))
     )
     

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152. new CompositeWorkflow<>(
     // Start in the AuthWorkflow. When it finishes, kick off
     // a TicTacToe game.
     new WorkflowBinding<>(AuthWorkflow.class,
     () -> ignoreStartArg(authWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT))),
     // When a TicTacToe game ends, start another one.
     new WorkflowBinding<>(TicTacToeWorkflow.class,
     () -> ignoreStartArg(ticTacToeWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT)))
     )
     

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153. new CompositeWorkflow<>(
     // Start in the AuthWorkflow. When it finishes, kick off
     // a TicTacToe game.
     new WorkflowBinding<>(AuthWorkflow.class,
     () -> ignoreStartArg(authWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT))),
     // When a TicTacToe game ends, start another one.
     new WorkflowBinding<>(TicTacToeWorkflow.class,
     () -> ignoreStartArg(ticTacToeWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT)))
     )
     

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154. new CompositeWorkflow<>(
     // Start in the AuthWorkflow. When it finishes, kick off
     // a TicTacToe game.
     new WorkflowBinding<>(AuthWorkflow.class,
     () -> ignoreStartArg(authWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT))),
     // When a TicTacToe game ends, start another one.
     new WorkflowBinding<>(TicTacToeWorkflow.class,
     () -> ignoreStartArg(ticTacToeWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT)))
     )
     

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155. new CompositeWorkflow<>(
     // Start in the AuthWorkflow. When it finishes, kick off
     // a TicTacToe game.
     new WorkflowBinding<>(AuthWorkflow.class,
     () -> ignoreStartArg(authWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT))),
     // When a TicTacToe game ends, start another one.
     new WorkflowBinding<>(TicTacToeWorkflow.class,
     () -> ignoreStartArg(ticTacToeWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT)))
     )
     

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156. new CompositeWorkflow<>(
     // Start in the AuthWorkflow. When it finishes, kick off
     // a TicTacToe game.
     new WorkflowBinding<>(AuthWorkflow.class,
     () -> ignoreStartArg(authWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT))),
     // When a TicTacToe game ends, start another one.
     new WorkflowBinding<>(TicTacToeWorkflow.class,
     () -> ignoreStartArg(ticTacToeWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT)))
     )
     

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157. new CompositeWorkflow<>(
     // Start in the AuthWorkflow. When it finishes, kick off
     // a TicTacToe game.
     new WorkflowBinding<>(AuthWorkflow.class,
     () -> ignoreStartArg(authWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT))),
     // When a TicTacToe game ends, start another one.
     new WorkflowBinding<>(TicTacToeWorkflow.class,
     () -> ignoreStartArg(ticTacToeWorkflowProvider.get()),
     (composite, result) -> composite.startWorkflow(
     forArg(TicTacToeWorkflow.class, (Unit) UNIT)))
     )
     

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158. Master
     Status
     Detail1 Detail2 Detail3
     

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159. Tactics
     

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160. Step zero: make refactoring…
     …possible
     • Mock service layer
     • Robot-based UI tests (espresso, KIF)
     …tolerable
     • OkBuck for Android
     • CocoaPods for iOS
     

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161. Divide first, conquer later
     

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162. Always be writing
     PSAs
     Design docs (everyone, all the time)
     Policy docs (a few, mostly: “write a damn design doc”)
     How-to guides and sample code
     

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163. Full disclosure
     Brick pattern established on both
     First j2Objc brick entering production
     Non-toy workflows in development on both
     Composite Workflow on Android
     Composite WorkflowScreen TBD
     

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164. @rjrjr
     speakerdeck.com/rjrjr/where-the-reactive-rubber-meets-the-road
     Dan Lew transformer
     github.com/square/coordinators
     Andy Matuschak states (http://bfy.tw/E969)
     square.com/jobs
     

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