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reacting to code sprawl Reactive Workflows Ray Ryan

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Key-based MVP the legacy

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Key-based MVP Key flow.set(Key)

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Key-based MVP Key View

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Key-based MVP Key Presenter View

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Key-based MVP Key Presenter View Model Model Model

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Key-based MVP CartScreen Cart Presenter CartView Item Library Cart

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

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

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Key-based MVP ChargeScreen CartScreen

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

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

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

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Nav logic sprawl ChargeScreen CartScreen

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Nav logic sprawl ChargeScreen CartScreen TipScreen

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Nav logic sprawl ChargeScreen CartScreen TipScreen SignatureScreen

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Nav logic sprawl ChargeScreen CartScreen TipScreen SignatureScreen

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Nav logic sprawl ChargeScreen CartScreen TipScreen SignatureScreen ReceiptScreen

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Nav logic sprawl ChargeScreen CartScreen TipScreen SignatureScreen ReceiptScreen

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Nav logic sprawl ChargeScreen CartScreen TipScreen SignatureScreen ReceiptScreen

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Nav logic sprawl ChargeScreen CartScreen TipScreen SignatureScreen ReceiptScreen

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Nav logic sprawl ChargeScreen CartScreen TipScreen SignatureScreen ReceiptScreen Payment Runner

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Nav logic sprawl ChargeScreen CartScreen TipScreen SignatureScreen ReceiptScreen Payment Runner SettingsScreen

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

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

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

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

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

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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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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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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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AddCustomer Runner Awkward reuse Cart Presenter CartScreen Cart

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AddCustomer Runner Awkward reuse Cart Presenter start() CartScreen Cart

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

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AddCustomer Runner Awkward reuse Pick Customer Presenter PickCustomerScreen CartScreen Cart

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

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AddCustomer Runner Awkward reuse Receipt Presenter ReceiptScreen Receipt

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

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

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AddCustomer Runner Awkward reuse Pick Customer Presenter PickCustomerScreen ReceiptScreen

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

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

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

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

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Good enough don’t scale four years later

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

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

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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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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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Reclaiming the commons we bring glad tidings from the future

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

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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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Describe Utopia

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Describe Utopia

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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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“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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“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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Workflows and Bricks Brick

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Workflows and Bricks Bricks Business model i/o Brick

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

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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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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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“Brick” rhymes with “schmego” Brick

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“Brick” rhymes with “schmego”

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“Brick” rhymes with “schmego”

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

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

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

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

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

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Build big bricks from small bricks

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Build big bricks from small bricks

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Build big bricks from small bricks

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Build big bricks from small bricks j2Objc JavaScript

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enum class StateOfPlay { PLAYING, VICTORY, DRAW }

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

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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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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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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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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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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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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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class GameRunner {

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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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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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Workflow through the brickyard

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

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

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

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

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Presenter Runner + = Workflow

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

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

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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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LoginScreen AuthorizingScreen SecondFactorScreen

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

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

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

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

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

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

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

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class AuthWorkflow(): Workflow

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

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

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

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

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

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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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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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NewGameScreen GamePlayScreen GameOverScreen ConfirmQuitScreen

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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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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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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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class TicTacToeWorkflow( private val gameRunner: GameRunner ): Workflow

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

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

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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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RootView View Factory Container Workflow

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RootView View Factory Container Workflow

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RootView Key ScreenData Events WorkflowScreen View Factory Container Workflow

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RootView Key ScreenData Events WorkflowScreen View Factory Container Workflow

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RootView Key ScreenData Events WorkflowScreen View Factory Container Workflow

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RootView View Factory Container Workflow

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RootView Key ScreenData Events WorkflowScreen View Factory Container Workflow

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RootView View Factory Container Workflow

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Workflow You said these things compose

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Workflow You said these things compose Auth Workflow Game Workflow

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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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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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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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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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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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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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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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Master Status Detail1 Detail2 Detail3

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Tactics

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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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Divide first, conquer later

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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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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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@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