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Basically Redux - Android Listeners

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Cody Engel

The document outlines the fundamentals of Redux, including actions which convey data to the store, reducers that dictate how application state changes, and the store that consolidates actions and reducers. It also touches on concepts of data flow, finite-state machines, and pure functions, using a gumball machine as an illustrative example. The implementation details for the gumball machine involve various classes and methods to manage its state and functions like buying and refilling gumballs.

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“Basically Redux” Cody Engel @POTUS404 Senior Engineer
@POTUS404 Redux Basics
@POTUS404Redux Basics Actions Actions are payloads of information that send data from your application to your store. They are the only source of information for the store. Actions do not describe how the actions will change the state. https://redux.js.org/basics/actions
@POTUS404Redux Basics Actions { type: ADD_TODO, text: 'Build my first Redux app' }
@POTUS404Redux Basics Reducers Reducers specify how the application's state changes in response to actions sent to the store. Remember that actions only describe what happened, but don't describe how the application's state changes. https://redux.js.org/basics/reducers
@POTUS404Redux Basics Reducers function todoApp(state = initialState, action) { switch (action.type) { case SET_VISIBILITY_FILTER: return Object.assign({}, state, { visibilityFilter: action.filter }) default: return state } }
@POTUS404Redux Basics The Store The Store brings the actions and reducers together. It holds the application’s state and allows state to be updated and observed on. You’ll only ever have one store in a Redux application. https://redux.js.org/basics/store
@POTUS404Redux Basics Data Flow Redux follows a strict unidirectional data flow. This means data in your systems follows a predictable path which is easier to understand. https://redux.js.org/basics/data-flow
@POTUS404Redux Basics Data Flow Actions Reducers Store State Tree Updated
@POTUS404 Algebraic Data Types
@POTUS404Algebraic Data Types Product Type A product type is a structure made up of multiple other types.
@POTUS404Algebraic Data Types Product Type data class Gumball( val size: GumballSize, val color: GumballColor )
@POTUS404Algebraic Data Types Sum Type A structure used to hold a value that could take on several different, but fixed types.
@POTUS404Algebraic Data Types Sum Type sealed class GumballSize { object Small : GumballSize() object Medium : GumballSize() object Large : GumballSize() }
@POTUS404 Pure Functions
@POTUS404Pure Functions Pure Functions A pure function is a function where the return value is only determined by its input values, without observable side effects.
@POTUS404Pure Functions fun add(left: Int, right: Int): Int { return left + right } Pure Functions
@POTUS404Pure Functions fun giveMeAGumball( gumballSize: GumballSize, gumballColor: GumballColor ): Gumball { return Gumball(gumballSize, gumballColor) } Pure Functions
@POTUS404 Finite-state Machines
@POTUS404Finite-state Machine A finite state machine is one that has a limited or finite number of possible states. Finite-state Machines
@POTUS404Finite-state Machines
@POTUS404 • How many gumballs are left? • Is it currently dispensing? Gumball Machine States Finite-state Machines
@POTUS404 REDUCE!
@POTUS404REDUCE! fun main(args: Array<String>) { val gumballMachine = GumballMachine() while(true) { if (gumballMachine.hasGumballs) { println("Purchased a ${gumballMachine.buyGumball()}") } else { println("Sorry, no more gumballs.") print("Would you like to refill the gumball machine? y/n: ") if (readLine() == "y") { gumballMachine.refill() println() } else { return } } } } Gumball Machine Usage
@POTUS404REDUCE! fun main(args: Array<String>) { val gumballMachine = GumballMachine() while(true) { if (gumballMachine.hasGumballs) { println("Purchased a ${gumballMachine.buyGumball()}") } else { println("Sorry, no more gumballs.") print("Would you like to refill the gumball machine? y/n: ") if (readLine() == "y") { gumballMachine.refill() println() } else { return } } } } Gumball Machine Usage
@POTUS404REDUCE! fun main(args: Array<String>) { val gumballMachine = GumballMachine() while(true) { if (gumballMachine.hasGumballs) { println("Purchased a ${gumballMachine.buyGumball()}") } else { println("Sorry, no more gumballs.") print("Would you like to refill the gumball machine? y/n: ") if (readLine() == "y") { gumballMachine.refill() println() } else { return } } } } Gumball Machine Usage
@POTUS404REDUCE! fun main(args: Array<String>) { val gumballMachine = GumballMachine() while(true) { if (gumballMachine.hasGumballs) { println("Purchased a ${gumballMachine.buyGumball()}") } else { println("Sorry, no more gumballs.") print("Would you like to refill the gumball machine? y/n: ") if (readLine() == "y") { gumballMachine.refill() println() } else { return } } } } Gumball Machine Usage
@POTUS404REDUCE! fun main(args: Array<String>) { val gumballMachine = GumballMachine() while(true) { if (gumballMachine.hasGumballs) { println("Purchased a ${gumballMachine.buyGumball()}") } else { println("Sorry, no more gumballs.") print("Would you like to refill the gumball machine? y/n: ") if (readLine() == "y") { gumballMachine.refill() println() } else { return } } } } Gumball Machine Usage
@POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
@POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
@POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } }
@POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
@POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
@POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
@POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
@POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
@POTUS404REDUCE! sealed class GumballAction : Action { object BuyGumball : GumballAction() object RefillGumballs : GumballAction() object Dispensed : GumballAction() } The Gumball Actions
@POTUS404REDUCE! data class GumballState( val remainingGumballs: Int = 100, val isDispensing: Boolean = false ) : State The Gumball State
@POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState { return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
@POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState{ return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
@POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState { return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
@POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState { return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
@POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState { return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
@POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState { return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
@POTUS404 RxJava
@POTUS404RxJava Observable.fromPublisher<CompanyAction> { subscriber -> 0.until(320).map { if (it % 11 == 0) CompanyAction.Add(Requisition.requisition) else CompanyAction.Hire(Requisition.requisition, Employee.employee) }.forEach { subscriber.onNext(it) }.also { subscriber.onComplete() } } .reduceWith({ Company("ActiveCampaign") }, { prevState, action -> when(action) { is CompanyAction.Hire -> { val employees = prevState.employees.toMutableList() employees.add(action.employee) prevState.copy(employees = employees) } is CompanyAction.Add -> { val requisitions = prevState.requisitions.toMutableList() requisitions.add(action.requisition) prevState.copy(requisitions = requisitions) } } }) .subscribe { state -> println("These numbers are most likely inaccurate.") println("ActiveCampaign has ${state.requisitions.size} job openings with around ${state.employees.size} employees.") println("There are ${state.employees.filter { it.name == "Cody" }.size} employees named Cody.") println("Here is the raw state output:") println(state) }
@POTUS404RxJava Observable.fromPublisher<CompanyAction> { subscriber -> 0.until(320).map { if (it % 11 == 0) CompanyAction.Add(Requisition.requisition) else CompanyAction.Hire(Requisition.requisition, Employee.employee) } .forEach { subscriber.onNext(it) } .also { subscriber.onComplete() } } .reduceWith({ Company("ActiveCampaign") }, { prevState, action -> when(action) { is CompanyAction.Hire -> { val employees = prevState.employees.toMutableList() employees.add(action.employee) prevState.copy(employees = employees) } is CompanyAction.Add -> { val requisitions = prevState.requisitions.toMutableList() requisitions.add(action.requisition) prevState.copy(requisitions = requisitions) } } }) .subscribe { state -> println("These numbers are most likely inaccurate.") println("ActiveCampaign has ${state.requisitions.size} job openings with around ${state.employees.size} employees.") println("There are ${state.employees.filter { it.name == "Cody" }.size} employees named Cody.") println("Here is the raw state output:") println(state) }
@POTUS404RxJava Observable.fromPublisher<CompanyAction> { subscriber -> 0.until(320).map { if (it % 11 == 0) CompanyAction.Add(Requisition.requisition) else CompanyAction.Hire(Requisition.requisition, Employee.employee) }.forEach { subscriber.onNext(it) }.also { subscriber.onComplete() } } .reduceWith({ Company("ActiveCampaign") }, { prevState, action -> when(action) { is CompanyAction.Hire -> { val employees = prevState.employees.toMutableList() employees.add(action.employee) prevState.copy(employees = employees) } is CompanyAction.Add -> { val requisitions = prevState.requisitions.toMutableList() requisitions.add(action.requisition) prevState.copy(requisitions = requisitions) } } }) .subscribe { state -> println("These numbers are most likely inaccurate.") println("ActiveCampaign has ${state.requisitions.size} job openings with around ${state.employees.size} employees.") println("There are ${state.employees.filter { it.name == "Cody" }.size} employees named Cody.") println("Here is the raw state output:") println(state) }
@POTUS404RxJava Observable.fromPublisher<CompanyAction> { subscriber -> 0.until(320).map { if (it % 11 == 0) CompanyAction.Add(Requisition.requisition) else CompanyAction.Hire(Requisition.requisition, Employee.employee) }.forEach { subscriber.onNext(it) }.also { subscriber.onComplete() } } .reduceWith({ Company("ActiveCampaign") }, { prevState, action -> when(action) { is CompanyAction.Hire -> { val employees = prevState.employees.toMutableList() employees.add(action.employee) prevState.copy(employees = employees) } is CompanyAction.Add -> { val requisitions = prevState.requisitions.toMutableList() requisitions.add(action.requisition) prevState.copy(requisitions = requisitions) } } }) .subscribe { state -> println("These numbers are most likely inaccurate.") println("ActiveCampaign has ${state.requisitions.size} job openings with around ${state.employees.size} employees.") println("There are ${state.employees.filter { it.name == "Cody" }.size} employees named Cody.") println("Here is the raw state output:") println(state) }
These numbers are most likely inaccurate. ActiveCampaign has 30 job openings with around 290 employees. There are 19 employees named Cody. Here is the raw state output: Company(name=ActiveCampaign, requisitions=[Requisition(name=Full Stack Engineer, department=Engineering), …) @POTUS404RxJava
Cody Engel @POTUS404 Senior Engineer (We’re Hiring) Thanks!

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Basically Redux - Android Listeners

  • 3. @POTUS404Redux Basics Actions Actions are payloads of information that send data from your application to your store. They are the only source of information for the store. Actions do not describe how the actions will change the state. https://redux.js.org/basics/actions
  • 5. @POTUS404Redux Basics Reducers Reducers specify how the application's state changes in response to actions sent to the store. Remember that actions only describe what happened, but don't describe how the application's state changes. https://redux.js.org/basics/reducers
  • 6. @POTUS404Redux Basics Reducers function todoApp(state = initialState, action) { switch (action.type) { case SET_VISIBILITY_FILTER: return Object.assign({}, state, { visibilityFilter: action.filter }) default: return state } }
  • 7. @POTUS404Redux Basics The Store The Store brings the actions and reducers together. It holds the application’s state and allows state to be updated and observed on. You’ll only ever have one store in a Redux application. https://redux.js.org/basics/store
  • 8. @POTUS404Redux Basics Data Flow Redux follows a strict unidirectional data flow. This means data in your systems follows a predictable path which is easier to understand. https://redux.js.org/basics/data-flow
  • 9. @POTUS404Redux Basics Data Flow Actions Reducers Store State Tree Updated
  • 11. @POTUS404Algebraic Data Types Product Type A product type is a structure made up of multiple other types.
  • 12. @POTUS404Algebraic Data Types Product Type data class Gumball( val size: GumballSize, val color: GumballColor )
  • 13. @POTUS404Algebraic Data Types Sum Type A structure used to hold a value that could take on several different, but fixed types.
  • 14. @POTUS404Algebraic Data Types Sum Type sealed class GumballSize { object Small : GumballSize() object Medium : GumballSize() object Large : GumballSize() }
  • 16. @POTUS404Pure Functions Pure Functions A pure function is a function where the return value is only determined by its input values, without observable side effects.
  • 17. @POTUS404Pure Functions fun add(left: Int, right: Int): Int { return left + right } Pure Functions
  • 18. @POTUS404Pure Functions fun giveMeAGumball( gumballSize: GumballSize, gumballColor: GumballColor ): Gumball { return Gumball(gumballSize, gumballColor) } Pure Functions
  • 20. @POTUS404Finite-state Machine A finite state machine is one that has a limited or finite number of possible states. Finite-state Machines
  • 22. @POTUS404 • How many gumballs are left? • Is it currently dispensing? Gumball Machine States Finite-state Machines
  • 24. @POTUS404REDUCE! fun main(args: Array<String>) { val gumballMachine = GumballMachine() while(true) { if (gumballMachine.hasGumballs) { println("Purchased a ${gumballMachine.buyGumball()}") } else { println("Sorry, no more gumballs.") print("Would you like to refill the gumball machine? y/n: ") if (readLine() == "y") { gumballMachine.refill() println() } else { return } } } } Gumball Machine Usage
  • 25. @POTUS404REDUCE! fun main(args: Array<String>) { val gumballMachine = GumballMachine() while(true) { if (gumballMachine.hasGumballs) { println("Purchased a ${gumballMachine.buyGumball()}") } else { println("Sorry, no more gumballs.") print("Would you like to refill the gumball machine? y/n: ") if (readLine() == "y") { gumballMachine.refill() println() } else { return } } } } Gumball Machine Usage
  • 26. @POTUS404REDUCE! fun main(args: Array<String>) { val gumballMachine = GumballMachine() while(true) { if (gumballMachine.hasGumballs) { println("Purchased a ${gumballMachine.buyGumball()}") } else { println("Sorry, no more gumballs.") print("Would you like to refill the gumball machine? y/n: ") if (readLine() == "y") { gumballMachine.refill() println() } else { return } } } } Gumball Machine Usage
  • 27. @POTUS404REDUCE! fun main(args: Array<String>) { val gumballMachine = GumballMachine() while(true) { if (gumballMachine.hasGumballs) { println("Purchased a ${gumballMachine.buyGumball()}") } else { println("Sorry, no more gumballs.") print("Would you like to refill the gumball machine? y/n: ") if (readLine() == "y") { gumballMachine.refill() println() } else { return } } } } Gumball Machine Usage
  • 28. @POTUS404REDUCE! fun main(args: Array<String>) { val gumballMachine = GumballMachine() while(true) { if (gumballMachine.hasGumballs) { println("Purchased a ${gumballMachine.buyGumball()}") } else { println("Sorry, no more gumballs.") print("Would you like to refill the gumball machine? y/n: ") if (readLine() == "y") { gumballMachine.refill() println() } else { return } } } } Gumball Machine Usage
  • 29. @POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
  • 30. @POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
  • 31. @POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } }
  • 32. @POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
  • 33. @POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
  • 34. @POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
  • 35. @POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
  • 36. @POTUS404REDUCE! The Gumball Machine class GumballMachine(private val timeToDispense: Long = 50) { object Gumball { override fun toString() = "$color Gumball" private val color get() = when(Random().nextInt(8) + 1) { 1 -> "Blue" 2 -> "Red" 3 -> "Green" 4 -> "Yellow" 5 -> "Pink" 6 -> "Purple" 7 -> "Orange" else -> "White" } } val hasGumballs get() = state.remainingGumballs > 0 private val gumballReducer = GumballReducer() private var state = GumballState() fun buyGumball(): Gumball { state = gumballReducer.reduce(state, GumballAction.BuyGumball) Thread.sleep(timeToDispense) state = gumballReducer.reduce(state, GumballAction.Dispensed) return Gumball } fun refill() { state = gumballReducer.reduce(state, GumballAction.RefillGumballs) } }
  • 37. @POTUS404REDUCE! sealed class GumballAction : Action { object BuyGumball : GumballAction() object RefillGumballs : GumballAction() object Dispensed : GumballAction() } The Gumball Actions
  • 38. @POTUS404REDUCE! data class GumballState( val remainingGumballs: Int = 100, val isDispensing: Boolean = false ) : State The Gumball State
  • 39. @POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState { return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
  • 40. @POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState{ return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
  • 41. @POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState { return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
  • 42. @POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState { return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
  • 43. @POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState { return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
  • 44. @POTUS404REDUCE! class GumballReducer : Reducer<GumballState, GumballAction> { override fun reduce(state: GumballState, action: GumballAction): GumballState { return when(action) { is GumballAction.BuyGumball -> { if (state.isDispensing) { throw IllegalStateException(“…”) } else if (state.remainingGumballs <= 0) { throw IllegalStateException(“…”) } state.copy( remainingGumballs = state.remainingGumballs - 1, isDispensing = true ) } is GumballAction.RefillGumballs -> state.copy( remainingGumballs = 100, isDispensing = false ) is GumballAction.Dispensed -> state.copy(isDispensing = false) } } } The Gumball Reducer
  • 46. @POTUS404RxJava Observable.fromPublisher<CompanyAction> { subscriber -> 0.until(320).map { if (it % 11 == 0) CompanyAction.Add(Requisition.requisition) else CompanyAction.Hire(Requisition.requisition, Employee.employee) }.forEach { subscriber.onNext(it) }.also { subscriber.onComplete() } } .reduceWith({ Company("ActiveCampaign") }, { prevState, action -> when(action) { is CompanyAction.Hire -> { val employees = prevState.employees.toMutableList() employees.add(action.employee) prevState.copy(employees = employees) } is CompanyAction.Add -> { val requisitions = prevState.requisitions.toMutableList() requisitions.add(action.requisition) prevState.copy(requisitions = requisitions) } } }) .subscribe { state -> println("These numbers are most likely inaccurate.") println("ActiveCampaign has ${state.requisitions.size} job openings with around ${state.employees.size} employees.") println("There are ${state.employees.filter { it.name == "Cody" }.size} employees named Cody.") println("Here is the raw state output:") println(state) }
  • 47. @POTUS404RxJava Observable.fromPublisher<CompanyAction> { subscriber -> 0.until(320).map { if (it % 11 == 0) CompanyAction.Add(Requisition.requisition) else CompanyAction.Hire(Requisition.requisition, Employee.employee) } .forEach { subscriber.onNext(it) } .also { subscriber.onComplete() } } .reduceWith({ Company("ActiveCampaign") }, { prevState, action -> when(action) { is CompanyAction.Hire -> { val employees = prevState.employees.toMutableList() employees.add(action.employee) prevState.copy(employees = employees) } is CompanyAction.Add -> { val requisitions = prevState.requisitions.toMutableList() requisitions.add(action.requisition) prevState.copy(requisitions = requisitions) } } }) .subscribe { state -> println("These numbers are most likely inaccurate.") println("ActiveCampaign has ${state.requisitions.size} job openings with around ${state.employees.size} employees.") println("There are ${state.employees.filter { it.name == "Cody" }.size} employees named Cody.") println("Here is the raw state output:") println(state) }
  • 48. @POTUS404RxJava Observable.fromPublisher<CompanyAction> { subscriber -> 0.until(320).map { if (it % 11 == 0) CompanyAction.Add(Requisition.requisition) else CompanyAction.Hire(Requisition.requisition, Employee.employee) }.forEach { subscriber.onNext(it) }.also { subscriber.onComplete() } } .reduceWith({ Company("ActiveCampaign") }, { prevState, action -> when(action) { is CompanyAction.Hire -> { val employees = prevState.employees.toMutableList() employees.add(action.employee) prevState.copy(employees = employees) } is CompanyAction.Add -> { val requisitions = prevState.requisitions.toMutableList() requisitions.add(action.requisition) prevState.copy(requisitions = requisitions) } } }) .subscribe { state -> println("These numbers are most likely inaccurate.") println("ActiveCampaign has ${state.requisitions.size} job openings with around ${state.employees.size} employees.") println("There are ${state.employees.filter { it.name == "Cody" }.size} employees named Cody.") println("Here is the raw state output:") println(state) }
  • 49. @POTUS404RxJava Observable.fromPublisher<CompanyAction> { subscriber -> 0.until(320).map { if (it % 11 == 0) CompanyAction.Add(Requisition.requisition) else CompanyAction.Hire(Requisition.requisition, Employee.employee) }.forEach { subscriber.onNext(it) }.also { subscriber.onComplete() } } .reduceWith({ Company("ActiveCampaign") }, { prevState, action -> when(action) { is CompanyAction.Hire -> { val employees = prevState.employees.toMutableList() employees.add(action.employee) prevState.copy(employees = employees) } is CompanyAction.Add -> { val requisitions = prevState.requisitions.toMutableList() requisitions.add(action.requisition) prevState.copy(requisitions = requisitions) } } }) .subscribe { state -> println("These numbers are most likely inaccurate.") println("ActiveCampaign has ${state.requisitions.size} job openings with around ${state.employees.size} employees.") println("There are ${state.employees.filter { it.name == "Cody" }.size} employees named Cody.") println("Here is the raw state output:") println(state) }
  • 50. These numbers are most likely inaccurate. ActiveCampaign has 30 job openings with around 290 employees. There are 19 employees named Cody. Here is the raw state output: Company(name=ActiveCampaign, requisitions=[Requisition(name=Full Stack Engineer, department=Engineering), …) @POTUS404RxJava