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JazzCon 2017: State, Side Effects, and Redux. Oh my!

JazzCon 2017: State, Side Effects, and Redux. Oh my!

Jeremy Fairbank

March 23, 2017
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  1. State,
    Side Effects,
    and Redux
    Oh my!
    Jeremy Fairbank
    @elpapapollo / jfairbank

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  2. sigient.com

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  3. State

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  4. Controller
    View
    Model
    Model
    Model
    Model
    Model
    View
    View
    View
    View
    MVC

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  5. View
    Model
    Model
    Model
    Model
    Model
    View
    Model
    View
    Model
    View
    Model
    View
    Model
    Model
    Two-way Data Binding

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  6. Disorganized Changes
    {...}

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  7. ?

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  9. Redux
    Unidirectional
    Organized changes
    Read-only state

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  10. Reducer
    View
    State
    Actions

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  11. Reducer
    View
    State
    Actions

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  12. Reducer
    View
    State
    Actions

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  13. Reducer
    View
    React,
    Angular,
    Vue,
    Vanilla JS,
    etc.
    State
    Actions

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  14. Reducer
    View
    State
    Actions
    Dispatch

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  15. Reducer
    View
    State
    Actions
    Repeat

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  16. Store
    Reducer
    State
    View

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  17. Store
    Reducer
    State
    View

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  18. Store
    Reducer
    State
    View

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  19. Store
    Reducer
    State
    View

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  20. Store
    Reducer
    State
    View
    Action

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  21. Store
    Reducer
    State
    View
    Action

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  22. Store
    Reducer
    State
    View

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  23. Store
    Reducer
    State
    View

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  24. Store
    Reducer
    State
    View

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  25. Store
    Reducer
    State
    View

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  26. let state = 0;
    incrementBtn.addEventListener('click', () => {
    state += 1;
    });
    decrementBtn.addEventListener('click', () => {
    state -= 1;
    });

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  27. let state = 0;
    incrementBtn.addEventListener('click', () => {
    state += 1;
    });
    decrementBtn.addEventListener('click', () => {
    state -= 1;
    });

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  28. let state = 0;
    incrementBtn.addEventListener('click', () => {
    state += 1;
    });
    decrementBtn.addEventListener('click', () => {
    state -= 1;
    });

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  29. let state = 0;
    state += 1;
    state += 1;
    state -= 1;
    console.log(state); // 1

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  30. let state = 0;
    state += 1;
    state += 1;
    state -= 1;
    console.log(state); // 1

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  31. let state = 0;
    state += 1;
    state += 1;
    state -= 1;
    console.log(state); // 1
    { type: 'INCREMENT' };
    { type: 'INCREMENT' };
    { type: 'DECREMENT' };

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  32. let state = 0;
    state += 1;
    state += 1;
    state -= 1;
    console.log(state); // 1
    { type: 'INCREMENT' };
    { type: 'INCREMENT' };
    { type: 'DECREMENT' };
    Action

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  33. Reducer

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  34. let state = 0;
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'DECREMENT' });
    console.log(state); // 1

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  35. let state = 0;
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'DECREMENT' });
    console.log(state); // 1

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  36. let state = 0;
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'DECREMENT' });
    console.log(state); // 1

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  37. let state = 0;
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'DECREMENT' });
    console.log(state); // 1

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  38. let state = 0;
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'DECREMENT' });
    console.log(state); // 1
    Action

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  39. let state = 0;
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'DECREMENT' });
    console.log(state); // 1

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  40. let state = 0;
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'DECREMENT' });
    console.log(state); // 1

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  41. let state = 0;
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'DECREMENT' });
    console.log(state); // 1

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  42. let state = 0;
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'INCREMENT' });
    state = reducer(state, { type: 'DECREMENT' });
    console.log(state); // 1

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  43. function reducer(state = 0, action) {
    switch (action.type) {
    case 'INCREMENT':
    return state + 1;
    case 'DECREMENT':
    return state - 1;
    default:
    return state;
    }
    }

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  44. function reducer(state = 0, action) {
    switch (action.type) {
    case 'INCREMENT':
    return state + 1;
    case 'DECREMENT':
    return state - 1;
    default:
    return state;
    }
    }

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  45. function reducer(state = 0, action) {
    switch (action.type) {
    case 'INCREMENT':
    return state + 1;
    case 'DECREMENT':
    return state - 1;
    default:
    return state;
    }
    }

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  46. function reducer(state = 0, action) {
    switch (action.type) {
    case 'INCREMENT':
    return state + 1;
    case 'DECREMENT':
    return state - 1;
    default:
    return state;
    }
    }

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  47. function reducer(state = 0, action) {
    switch (action.type) {
    case 'INCREMENT':
    return state + 1;
    case 'DECREMENT':
    return state - 1;
    default:
    return state;
    }
    }

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  48. function reducer(state = 0, action) {
    switch (action.type) {
    case 'INCREMENT':
    return state + 1;
    case 'DECREMENT':
    return state - 1;
    default:
    return state;
    }
    }

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  49. function reducer(state = 0, action) {
    switch (action.type) {
    case 'INCREMENT':
    return state + 1;
    case 'DECREMENT':
    return state - 1;
    default:
    return state;
    }
    }

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  50. Store

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  51. import { createStore } from 'redux';
    const store = createStore(reducer);
    store.getState(); // 0

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  52. import { createStore } from 'redux';
    const store = createStore(reducer);
    store.getState(); // 0

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  53. import { createStore } from 'redux';
    const store = createStore(reducer);
    store.getState(); // 0

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  54. import { createStore } from 'redux';
    const store = createStore(reducer);
    store.getState(); // 0

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  55. store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'DECREMENT' });
    store.getState(); // 1

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  56. store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'DECREMENT' });
    store.getState(); // 1

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  57. store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'DECREMENT' });
    store.getState(); // 1

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  58. store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'DECREMENT' });
    store.getState(); // 1

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  59. store.subscribe(() => {
    console.log('state =', store.getState());
    });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'DECREMENT' });
    // state = 1
    // state = 2
    // state = 1

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  60. store.subscribe(() => {
    console.log('state =', store.getState());
    });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'DECREMENT' });
    // state = 1
    // state = 2
    // state = 1

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  61. store.subscribe(() => {
    console.log('state =', store.getState());
    });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'DECREMENT' });
    // state = 1
    // state = 2
    // state = 1

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  62. store.subscribe(() => {
    console.log('state =', store.getState());
    });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'INCREMENT' });
    store.dispatch({ type: 'DECREMENT' });
    // state = 1
    // state = 2
    // state = 1

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  63. Action
    Creators

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  64. const increment = () => ({
    type: 'INCREMENT',
    });
    const decrement = () => ({
    type: 'DECREMENT',
    });

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  65. const increment = () => ({
    type: 'INCREMENT',
    });
    const decrement = () => ({
    type: 'DECREMENT',
    });

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  66. const increment = () => ({
    type: 'INCREMENT',
    });
    const decrement = () => ({
    type: 'DECREMENT',
    });

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  67. const unsubscribe = store.subscribe(() => {
    console.log('state =', store.getState());
    });
    store.dispatch(increment());
    store.dispatch(increment());
    store.dispatch(decrement());
    // state = 1
    // state = 2
    // state = 1

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  68. const unsubscribe = store.subscribe(() => {
    console.log('state =', store.getState());
    });
    store.dispatch(increment());
    store.dispatch(increment());
    store.dispatch(decrement());
    // state = 1
    // state = 2
    // state = 1

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  69. import { bindActionCreators } from 'redux';
    const actions = bindActionCreators(
    { increment, decrement },
    store.dispatch
    );
    actions.increment();
    actions.increment();
    actions.decrement();
    // state = 1
    // state = 2
    // state = 1

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  70. import { bindActionCreators } from 'redux';
    const actions = bindActionCreators(
    { increment, decrement },
    store.dispatch
    );
    actions.increment();
    actions.increment();
    actions.decrement();
    // state = 1
    // state = 2
    // state = 1

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  71. import { bindActionCreators } from 'redux';
    const actions = bindActionCreators(
    { increment, decrement },
    store.dispatch
    );
    actions.increment();
    actions.increment();
    actions.decrement();
    // state = 1
    // state = 2
    // state = 1

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  72. import { bindActionCreators } from 'redux';
    const actions = bindActionCreators(
    { increment, decrement },
    store.dispatch
    );
    actions.increment();
    actions.increment();
    actions.decrement();
    // state = 1
    // state = 2
    // state = 1

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  73. import { bindActionCreators } from 'redux';
    const actions = bindActionCreators(
    { increment, decrement },
    store.dispatch
    );
    actions.increment();
    actions.increment();
    actions.decrement();
    // state = 1
    // state = 2
    // state = 1

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  74. incrementBtn.addEventListener('click', actions.increment);
    decrementBtn.addEventListener('click', actions.decrement);
    store.subscribe(() => {
    counterElement.innerHTML = store.getState();
    });
    incrementBtn.click();
    incrementBtn.click();
    decrementBtn.click();
    console.log(counterElement.innerHTML); // 1

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  75. incrementBtn.addEventListener('click', actions.increment);
    decrementBtn.addEventListener('click', actions.decrement);
    store.subscribe(() => {
    counterElement.innerHTML = store.getState();
    });
    incrementBtn.click();
    incrementBtn.click();
    decrementBtn.click();
    console.log(counterElement.innerHTML); // 1

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  76. incrementBtn.addEventListener('click', actions.increment);
    decrementBtn.addEventListener('click', actions.decrement);
    store.subscribe(() => {
    counterElement.innerHTML = store.getState();
    });
    incrementBtn.click();
    incrementBtn.click();
    decrementBtn.click();
    console.log(counterElement.innerHTML); // 1

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  77. incrementBtn.addEventListener('click', actions.increment);
    decrementBtn.addEventListener('click', actions.decrement);
    store.subscribe(() => {
    counterElement.innerHTML = store.getState();
    });
    incrementBtn.click();
    incrementBtn.click();
    decrementBtn.click();
    console.log(counterElement.innerHTML); // 1

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  78. incrementBtn.addEventListener('click', actions.increment);
    decrementBtn.addEventListener('click', actions.decrement);
    store.subscribe(() => {
    counterElement.innerHTML = store.getState();
    });
    incrementBtn.click();
    incrementBtn.click();
    decrementBtn.click();
    console.log(counterElement.innerHTML); // 1

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  79. Immutable
    Object State

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  80. const initialState = {
    counter: 0,
    car: {
    color: 'red',
    },
    };

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  81. const initialState = {
    counter: 0,
    car: {
    color: 'red',
    },
    };

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  82. const initialState = {
    counter: 0,
    car: {
    color: 'red',
    },
    };

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  83. function reducer(state = initialState, action) {
    switch (action.type) {
    case 'INCREMENT':
    return { ...state, counter: state.counter + 1 };
    case 'DECREMENT':
    return { ...state, counter: state.counter - 1 };
    case 'CHANGE_COLOR':
    return { ...state, car: { color: action.payload } };
    default:
    return state;
    }
    }

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  84. function reducer(state = initialState, action) {
    switch (action.type) {
    case 'INCREMENT':
    return { ...state, counter: state.counter + 1 };
    case 'DECREMENT':
    return { ...state, counter: state.counter - 1 };
    case 'CHANGE_COLOR':
    return { ...state, car: { color: action.payload } };
    default:
    return state;
    }
    }

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  85. function reducer(state = initialState, action) {
    switch (action.type) {
    case 'INCREMENT':
    return { ...state, counter: state.counter + 1 };
    case 'DECREMENT':
    return { ...state, counter: state.counter - 1 };
    case 'CHANGE_COLOR':
    return { ...state, car: { color: action.payload } };
    default:
    return state;
    }
    }

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  86. function reducer(state = initialState, action) {
    switch (action.type) {
    case 'INCREMENT':
    return { ...state, counter: state.counter + 1 };
    case 'DECREMENT':
    return { ...state, counter: state.counter - 1 };
    case 'CHANGE_COLOR':
    return { ...state, car: { color: action.payload } };
    default:
    return state;
    }
    }

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  87. function reducer(state = initialState, action) {
    switch (action.type) {
    case 'INCREMENT':
    return { ...state, counter: state.counter + 1 };
    case 'DECREMENT':
    return { ...state, counter: state.counter - 1 };
    case 'CHANGE_COLOR':
    return { ...state, car: { color: action.payload } };
    default:
    return state;
    }
    }

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  88. function reducer(state = initialState, action) {
    switch (action.type) {
    case 'INCREMENT':
    return { ...state, counter: state.counter + 1 };
    case 'DECREMENT':
    return { ...state, counter: state.counter - 1 };
    case 'CHANGE_COLOR':
    return { ...state, car: { color: action.payload } };
    default:
    return state;
    }
    }

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  89. const increment = () => ({
    type: 'INCREMENT',
    });
    const decrement = () => ({
    type: 'DECREMENT',
    });
    const changeColor = color => ({
    type: 'CHANGE_COLOR',
    payload: color,
    });

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  90. const increment = () => ({
    type: 'INCREMENT',
    });
    const decrement = () => ({
    type: 'DECREMENT',
    });
    const changeColor = color => ({
    type: 'CHANGE_COLOR',
    payload: color,
    });

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  91. const increment = () => ({
    type: 'INCREMENT',
    });
    const decrement = () => ({
    type: 'DECREMENT',
    });
    const changeColor = color => ({
    type: 'CHANGE_COLOR',
    payload: color,
    });

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  92. store.subscribe(() => {
    console.log('state =', store.getState());
    });
    store.dispatch(increment());
    store.dispatch(changeColor('green'));
    // state = { counter: 1, car: { color: 'red' } }
    // state = { counter: 1, car: { color: 'green' } }

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  93. store.subscribe(() => {
    console.log('state =', store.getState());
    });
    store.dispatch(increment());
    store.dispatch(changeColor('green'));
    // state = { counter: 1, car: { color: 'red' } }
    // state = { counter: 1, car: { color: 'green' } }

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  94. store.subscribe(() => {
    console.log('state =', store.getState());
    });
    store.dispatch(increment());
    store.dispatch(changeColor('green'));
    // state = { counter: 1, car: { color: 'red' } }
    // state = { counter: 1, car: { color: 'green' } }

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  95. Middleware

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  96. Reducer
    View
    State
    Actions
    Middleware

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  97. Reducer
    View
    State
    Actions
    Middleware
    Intercept

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  98. const logMiddleware = api => next => action => {
    console.log('dispatch', action);
    const result = next(action);
    console.log('state =', api.getState());
    return result;
    };

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  99. const logMiddleware = api => next => action => {
    console.log('dispatch', action);
    const result = next(action);
    console.log('state =', api.getState());
    return result;
    };

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  100. const logMiddleware = api => next => action => {
    console.log('dispatch', action);
    const result = next(action);
    console.log('state =', api.getState());
    return result;
    };

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  101. const logMiddleware = api => next => action => {
    console.log('dispatch', action);
    const result = next(action);
    console.log('state =', api.getState());
    return result;
    };

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  102. const logMiddleware = api => next => action => {
    console.log('dispatch', action);
    const result = next(action);
    console.log('state =', api.getState());
    return result;
    };

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  103. const logMiddleware = api => next => action => {
    console.log('dispatch', action);
    const result = next(action);
    console.log('state =', api.getState());
    return result;
    };

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  104. const logMiddleware = api => next => action => {
    console.log('dispatch', action);
    const result = next(action);
    console.log('state =', api.getState());
    return result;
    };

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  105. const logMiddleware = api => next => action => {
    console.log('dispatch', action);
    const result = next(action);
    console.log('state =', api.getState());
    return result;
    };

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  106. const logMiddleware = api => next => action => {
    console.log('dispatch', action);
    const result = next(action);
    console.log('state =', api.getState());
    return result;
    };

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  107. import { applyMiddleware } from 'redux';
    const store = createStore(
    reducer,
    applyMiddleware(logMiddleware)
    );
    store.dispatch(increment());
    store.dispatch(changeColor('green'));
    // dispatch { type: 'INCREMENT' }
    // state = { counter: 1, car: { color: 'red' } }
    // dispatch { type: 'CHANGE_COLOR', payload: 'green' }
    // state = { counter: 1, car: { color: 'green' } }

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  108. import { applyMiddleware } from 'redux';
    const store = createStore(
    reducer,
    applyMiddleware(logMiddleware)
    );
    store.dispatch(increment());
    store.dispatch(changeColor('green'));
    // dispatch { type: 'INCREMENT' }
    // state = { counter: 1, car: { color: 'red' } }
    // dispatch { type: 'CHANGE_COLOR', payload: 'green' }
    // state = { counter: 1, car: { color: 'green' } }

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  109. import { applyMiddleware } from 'redux';
    const store = createStore(
    reducer,
    applyMiddleware(logMiddleware)
    );
    store.dispatch(increment());
    store.dispatch(changeColor('green'));
    // dispatch { type: 'INCREMENT' }
    // state = { counter: 1, car: { color: 'red' } }
    // dispatch { type: 'CHANGE_COLOR', payload: 'green' }
    // state = { counter: 1, car: { color: 'green' } }

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  110. import { applyMiddleware } from 'redux';
    const store = createStore(
    reducer,
    applyMiddleware(logMiddleware)
    );
    store.dispatch(increment());
    store.dispatch(changeColor('green'));
    // dispatch { type: 'INCREMENT' }
    // state = { counter: 1, car: { color: 'red' } }
    // dispatch { type: 'CHANGE_COLOR', payload: 'green' }
    // state = { counter: 1, car: { color: 'green' } }

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  111. import { applyMiddleware } from 'redux';
    const store = createStore(
    reducer,
    applyMiddleware(logMiddleware)
    );
    store.dispatch(increment());
    store.dispatch(changeColor('green'));
    // dispatch { type: 'INCREMENT' }
    // state = { counter: 1, car: { color: 'red' } }
    // dispatch { type: 'CHANGE_COLOR', payload: 'green' }
    // state = { counter: 1, car: { color: 'green' } }

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  112. Side Effects
    I/O
    Mutable
    State

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  113. const initialState = {
    users: [],
    isFetching: false,
    };

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  114. function reducer(state = initialState, action) {
    switch (action.type) {
    case 'REQUEST_USERS':
    return { ...state, isFetching: true };
    case 'RECEIVE_USERS':
    return {
    ...state,
    isFetching: false,
    users: action.payload,
    };
    default:
    return state;
    }
    }

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  115. function reducer(state = initialState, action) {
    switch (action.type) {
    case 'REQUEST_USERS':
    return { ...state, isFetching: true };
    case 'RECEIVE_USERS':
    return {
    ...state,
    isFetching: false,
    users: action.payload,
    };
    default:
    return state;
    }
    }

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  116. function reducer(state = initialState, action) {
    switch (action.type) {
    case 'REQUEST_USERS':
    return { ...state, isFetching: true };
    case 'RECEIVE_USERS':
    return {
    ...state,
    isFetching: false,
    users: action.payload,
    };
    default:
    return state;
    }
    }

    View Slide

  117. const requestUsers = () => ({
    type: 'REQUEST_USERS',
    });
    const receiveUsers = users => ({
    type: 'RECEIVE_USERS',
    payload: users,
    });

    View Slide

  118. const thunkMiddleware = api => next => action => {
    if (typeof action === 'function') {
    return action(api.dispatch);
    }
    return next(action);
    };
    const store = createStore(
    reducer,
    applyMiddleware(thunkMiddleware)
    );

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  119. const thunkMiddleware = api => next => action => {
    if (typeof action === 'function') {
    return action(api.dispatch);
    }
    return next(action);
    };
    const store = createStore(
    reducer,
    applyMiddleware(thunkMiddleware)
    );

    View Slide

  120. const thunkMiddleware = api => next => action => {
    if (typeof action === 'function') {
    return action(api.dispatch);
    }
    return next(action);
    };
    const store = createStore(
    reducer,
    applyMiddleware(thunkMiddleware)
    );

    View Slide

  121. const thunkMiddleware = api => next => action => {
    if (typeof action === 'function') {
    return action(api.dispatch);
    }
    return next(action);
    };
    const store = createStore(
    reducer,
    applyMiddleware(thunkMiddleware)
    );

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  122. function fetchUsers() {
    return dispatch => {
    dispatch(requestUsers());
    return axios.get('/users')
    .then(({ data }) => {
    dispatch(receiveUsers(data));
    });
    };
    }
    store.dispatch(fetchUsers());

    View Slide

  123. function fetchUsers() {
    return dispatch => {
    dispatch(requestUsers());
    return axios.get('/users')
    .then(({ data }) => {
    dispatch(receiveUsers(data));
    });
    };
    }
    store.dispatch(fetchUsers());
    Action Creator

    View Slide

  124. function fetchUsers() {
    return dispatch => {
    dispatch(requestUsers());
    return axios.get('/users')
    .then(({ data }) => {
    dispatch(receiveUsers(data));
    });
    };
    }
    store.dispatch(fetchUsers());
    Action

    View Slide

  125. function fetchUsers() {
    return dispatch => {
    dispatch(requestUsers());
    return axios.get('/users')
    .then(({ data }) => {
    dispatch(receiveUsers(data));
    });
    };
    }
    store.dispatch(fetchUsers());

    View Slide

  126. View Slide

  127. Reducer
    View
    State
    Actions
    Middleware
    Redux
    Saga

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  128. Reducer
    View
    State
    Actions
    Middleware
    Redux
    Saga

    View Slide

  129. Reducer
    View
    State
    Actions
    Middleware
    Redux
    Saga

    View Slide

  130. Reducer
    View
    State
    Actions
    Middleware
    Redux
    Saga

    View Slide

  131. Effect Descriptors
    take('SOME_ACTION_TYPE')
    call(someAsyncFunction)
    put(someAction())
    fork(someSagaFunction)
    Just values

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  132. Redux Saga
    Sagas

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  133. Redux Saga
    Sagas

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  134. Redux Saga
    Sagas

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  135. Redux Saga
    Sagas
    IO
    APIs
    Console
    DB
    call, apply

    View Slide

  136. Redux Saga
    Sagas
    IO
    APIs
    Console
    DB
    call, apply
    call, apply,
    fork, spawn,
    join, cancel

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  137. Redux Saga
    Sagas
    IO
    APIs
    Console
    DB
    call, apply
    call, apply,
    fork, spawn,
    join, cancel
    Redux
    Store
    put, select, take

    View Slide

  138. Generator
    Functions

    View Slide

  139. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }

    View Slide

  140. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }

    View Slide

  141. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }

    View Slide

  142. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }

    View Slide

  143. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    const iterator = myGenerator();
    iterator.next();
    // { value: 'hello', done: false }

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  144. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    const iterator = myGenerator();
    iterator.next();
    // { value: 'hello', done: false }

    View Slide

  145. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    const iterator = myGenerator();
    iterator.next();
    // { value: 'hello', done: false }

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  146. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    const iterator = myGenerator();
    iterator.next();
    // { value: 'hello', done: false }

    View Slide

  147. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    const iterator = myGenerator();
    iterator.next();
    // { value: 'hello', done: false }

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  148. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    iterator.next();
    // { value: 'world', done: false }

    View Slide

  149. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    iterator.next();
    // { value: 'world', done: false }

    View Slide

  150. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    iterator.next(21);
    // { value: 42, done: true }

    View Slide

  151. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    iterator.next(21);
    // { value: 42, done: true }

    View Slide

  152. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    iterator.next(21);
    // { value: 42, done: true }

    View Slide

  153. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    iterator.next();
    // { value: undefined, done: true }

    View Slide

  154. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    iterator.next();
    // { value: undefined, done: true }

    View Slide

  155. function* myGenerator() {
    yield 'hello';
    const value = yield 'world';
    return value * 2;
    }
    iterator.next();
    // { value: undefined, done: true }

    View Slide

  156. import { call, put, take } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    store.dispatch(requestUsers());

    View Slide

  157. import { call, put, take } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    store.dispatch(requestUsers());

    View Slide

  158. import { call, put, take } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    store.dispatch(requestUsers());

    View Slide

  159. import { call, put, take } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    store.dispatch(requestUsers());

    View Slide

  160. import { call, put, take } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    store.dispatch(requestUsers());

    View Slide

  161. import { call, put, take } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    store.dispatch(requestUsers());

    View Slide

  162. import { call, put, take } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    store.dispatch(requestUsers());

    View Slide

  163. import { call, put, take } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    store.dispatch(requestUsers());

    View Slide

  164. import { call, put, take } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    store.dispatch(requestUsers());

    View Slide

  165. Saga
    Redux Saga
    yield take('REQUEST_USERS');
    1. Wait for action

    View Slide

  166. Saga
    Redux Saga
    View
    Middleware
    yield take('REQUEST_USERS');
    2. Receive action

    View Slide

  167. Saga
    Redux Saga
    yield call(axios.get, '/users');
    3. Call API

    View Slide

  168. const response =
    yield call(axios.get, '/users');
    Saga
    Redux Saga
    4. Receive response

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  169. Saga
    Redux Saga
    Reducer
    Redux
    Store
    yield put(
    receiveUsers(response.data)
    );
    5. Dispatch (put) action

    View Slide

  170. Set Up

    View Slide

  171. import createSagaMiddleware from 'redux-saga';
    const sagaMiddleware = createSagaMiddleware();
    const store = createStore(
    reducer,
    applyMiddleware(sagaMiddleware)
    );
    sagaMiddleware.run(fetchUsersSaga);

    View Slide

  172. import createSagaMiddleware from 'redux-saga';
    const sagaMiddleware = createSagaMiddleware();
    const store = createStore(
    reducer,
    applyMiddleware(sagaMiddleware)
    );
    sagaMiddleware.run(fetchUsersSaga);

    View Slide

  173. import createSagaMiddleware from 'redux-saga';
    const sagaMiddleware = createSagaMiddleware();
    const store = createStore(
    reducer,
    applyMiddleware(sagaMiddleware)
    );
    sagaMiddleware.run(fetchUsersSaga);

    View Slide

  174. import createSagaMiddleware from 'redux-saga';
    const sagaMiddleware = createSagaMiddleware();
    const store = createStore(
    reducer,
    applyMiddleware(sagaMiddleware)
    );
    sagaMiddleware.run(fetchUsersSaga);

    View Slide

  175. import createSagaMiddleware from 'redux-saga';
    const sagaMiddleware = createSagaMiddleware();
    const store = createStore(
    reducer,
    applyMiddleware(sagaMiddleware)
    );
    sagaMiddleware.run(fetchUsersSaga);

    View Slide

  176. Why Sagas?

    View Slide

  177. Business Logic Spread Out
    Component
    Thunk
    Service
    Service
    Component
    Reducer

    View Slide

  178. Business Logic Spread Out
    Component
    Thunk
    Service
    Service
    Component
    ×
    Reducer

    View Slide

  179. Business Logic Consolidated
    Saga Saga Saga
    Saga
    Saga
    Saga

    View Slide

  180. Testing

    View Slide

  181. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    const saga = fetchUsersSaga();
    it('waits for REQUEST_USERS', () => {
    const actual = saga.next().value;
    const expected = take('REQUEST_USERS');
    expect(actual).toEqual(expected);
    });

    View Slide

  182. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    const saga = fetchUsersSaga();
    it('waits for REQUEST_USERS', () => {
    const actual = saga.next().value;
    const expected = take('REQUEST_USERS');
    expect(actual).toEqual(expected);
    });

    View Slide

  183. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    const saga = fetchUsersSaga();
    it('waits for REQUEST_USERS', () => {
    const actual = saga.next().value;
    const expected = take('REQUEST_USERS');
    expect(actual).toEqual(expected);
    });

    View Slide

  184. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    const saga = fetchUsersSaga();
    it('waits for REQUEST_USERS', () => {
    const actual = saga.next().value;
    const expected = take('REQUEST_USERS');
    expect(actual).toEqual(expected);
    });

    View Slide

  185. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    const saga = fetchUsersSaga();
    it('waits for REQUEST_USERS', () => {
    const actual = saga.next().value;
    const expected = take('REQUEST_USERS');
    expect(actual).toEqual(expected);
    });

    View Slide

  186. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    // ...
    it('fetches users', () => {
    const actual = saga.next().value;
    const expected = call(axios.get, '/users');
    expect(actual).toEqual(expected);
    });

    View Slide

  187. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    // ...
    it('fetches users', () => {
    const actual = saga.next().value;
    const expected = call(axios.get, '/users');
    expect(actual).toEqual(expected);
    });

    View Slide

  188. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    // ...
    it('fetches users', () => {
    const actual = saga.next().value;
    const expected = call(axios.get, '/users');
    expect(actual).toEqual(expected);
    });

    View Slide

  189. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    // ...
    it('fetches users', () => {
    const actual = saga.next().value;
    const expected = call(axios.get, '/users');
    expect(actual).toEqual(expected);
    });

    View Slide

  190. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    it('dispatches the users', () => {
    const users = [{ name: 'Bob' }, { name: 'Alice' }];
    const response = { data: users };
    const actual = saga.next(response).value;
    const expected = put(receiveUsers(users));
    expect(actual).toEqual(expected);
    });

    View Slide

  191. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    it('dispatches the users', () => {
    const users = [{ name: 'Bob' }, { name: 'Alice' }];
    const response = { data: users };
    const actual = saga.next(response).value;
    const expected = put(receiveUsers(users));
    expect(actual).toEqual(expected);
    });

    View Slide

  192. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    it('dispatches the users', () => {
    const users = [{ name: 'Bob' }, { name: 'Alice' }];
    const response = { data: users };
    const actual = saga.next(response).value;
    const expected = put(receiveUsers(users));
    expect(actual).toEqual(expected);
    });

    View Slide

  193. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    it('dispatches the users', () => {
    const users = [{ name: 'Bob' }, { name: 'Alice' }];
    const response = { data: users };
    const actual = saga.next(response).value;
    const expected = put(receiveUsers(users));
    expect(actual).toEqual(expected);
    });

    View Slide

  194. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    it('dispatches the users', () => {
    const users = [{ name: 'Bob' }, { name: 'Alice' }];
    const response = { data: users };
    const actual = saga.next(response).value;
    const expected = put(receiveUsers(users));
    expect(actual).toEqual(expected);
    });

    View Slide

  195. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    it('dispatches the users', () => {
    const users = [{ name: 'Bob' }, { name: 'Alice' }];
    const response = { data: users };
    const actual = saga.next(response).value;
    const expected = put(receiveUsers(users));
    expect(actual).toEqual(expected);
    });

    View Slide

  196. Error
    Handling

    View Slide

  197. const initialState = {
    users: [],
    isFetching: false,
    error: null,
    };

    View Slide

  198. const initialState = {
    users: [],
    isFetching: false,
    error: null,
    };

    View Slide

  199. const failUsers = error => ({
    type: 'FAIL_USERS',
    error,
    });

    View Slide

  200. function reducer(state = initialState, action) {
    switch (action.type) {
    // ...
    case 'FAIL_USERS':
    return { ...state, error: action.error };
    // ...
    }
    }

    View Slide

  201. function reducer(state = initialState, action) {
    switch (action.type) {
    // ...
    case 'FAIL_USERS':
    return { ...state, error: action.error };
    // ...
    }
    }

    View Slide

  202. function fetchUsers() {
    return dispatch => {
    dispatch(requestUsers());
    return axios.get('/users')
    .then(({ data }) => {
    dispatch(receiveUsers(data));
    })
    .catch((e) => {
    dispatch(failUsers(e));
    });
    };
    }

    View Slide

  203. function fetchUsers() {
    return dispatch => {
    dispatch(requestUsers());
    return axios.get('/users')
    .then(({ data }) => {
    dispatch(receiveUsers(data));
    })
    .catch((e) => {
    dispatch(failUsers(e));
    });
    };
    }
    Swallowed
    without catch

    View Slide

  204. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }

    View Slide

  205. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    No swallowed errors

    View Slide

  206. function* fetchUsersSaga() {
    try {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    } catch (e) {
    yield put(failUsers(e));
    }
    }

    View Slide

  207. function* fetchUsersSaga() {
    try {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    } catch (e) {
    yield put(failUsers(e));
    }
    }

    View Slide

  208. function* fetchUsersSaga() {
    try {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    } catch (e) {
    yield put(failUsers(e));
    }
    }

    View Slide

  209. function* fetchUsersSaga() {
    try {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    } catch (e) {
    yield put(failUsers(e));
    }
    }

    View Slide

  210. Multiple
    Requests

    View Slide

  211. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const responses = yield [
    call(axios.get, '/users/1'),
    call(axios.get, '/users/2'),
    call(axios.get, '/users/3'),
    ];
    const users = responses.map(resp => resp.data);
    yield put(receiveUsers(users));
    }

    View Slide

  212. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const responses = yield [
    call(axios.get, '/users/1'),
    call(axios.get, '/users/2'),
    call(axios.get, '/users/3'),
    ];
    const users = responses.map(resp => resp.data);
    yield put(receiveUsers(users));
    }

    View Slide

  213. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const responses = yield [
    call(axios.get, '/users/1'),
    call(axios.get, '/users/2'),
    call(axios.get, '/users/3'),
    ];
    const users = responses.map(resp => resp.data);
    yield put(receiveUsers(users));
    }

    View Slide

  214. function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const responses = yield [
    call(axios.get, '/users/1'),
    call(axios.get, '/users/2'),
    call(axios.get, '/users/3'),
    ];
    const users = responses.map(resp => resp.data);
    yield put(receiveUsers(users));
    }

    View Slide

  215. Saga
    yield [
    call(axios.get, '/users/1'),
    call(axios.get, '/users/2'),
    call(axios.get, '/users/3'),
    ];
    // ...

    View Slide

  216. Saga
    yield [
    call(axios.get, '/users/1'),
    call(axios.get, '/users/2'),
    call(axios.get, '/users/3'),
    ];
    // ...
    1
    2
    3

    View Slide

  217. Saga
    yield [
    call(axios.get, '/users/1'),
    call(axios.get, '/users/2'),
    call(axios.get, '/users/3'),
    ];
    // ...
    1
    2
    3

    View Slide

  218. Saga
    yield [
    call(axios.get, '/users/1'),
    call(axios.get, '/users/2'),
    call(axios.get, '/users/3'),
    ];
    // ...
    1
    3

    View Slide

  219. Saga
    yield [
    call(axios.get, '/users/1'),
    call(axios.get, '/users/2'),
    call(axios.get, '/users/3'),
    ];
    // ...
    3

    View Slide

  220. Saga Helpers

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  221. function* fetchUsersSaga() {
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    while (true) {
    yield take('REQUEST_USERS');
    yield call(fetchUsersSaga);
    }
    }

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  222. function* fetchUsersSaga() {
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    while (true) {
    yield take('REQUEST_USERS');
    yield call(fetchUsersSaga);
    }
    }

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  223. import { takeEvery } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    yield takeEvery('REQUEST_USERS', fetchUsersSaga);
    }

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  224. import { takeEvery } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    yield takeEvery('REQUEST_USERS', fetchUsersSaga);
    }

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  225. import { takeEvery } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    yield takeEvery('REQUEST_USERS', fetchUsersSaga);
    }

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  226. import { takeEvery } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    yield takeEvery('REQUEST_USERS', fetchUsersSaga);
    }

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  227. import { takeEvery } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    yield takeEvery('REQUEST_USERS', fetchUsersSaga);
    }

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  228. mainSaga
    fetchUsersSaga
    yield takeEvery(
    'REQUEST_USERS',
    fetchUsersSaga
    );

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  229. View
    Middleware
    store.dispatch(
    requestUsers()
    );
    mainSaga
    fetchUsersSaga

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  230. mainSaga
    fetchUsersSaga
    fork

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  231. mainSaga
    fetchUsersSaga
    yield call(
    axios.get,
    '/users'
    );

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  232. mainSaga
    fetchUsersSaga
    const response =
    yield call(
    axios.get,
    '/users'
    );

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  233. mainSaga
    fetchUsersSaga
    yield put(
    receiveUsers(
    response.data
    )
    );
    Reducer
    Redux
    Store

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  234. mainSaga
    fetchUsersSaga
    yield takeEvery(
    'REQUEST_USERS',
    fetchUsersSaga
    );
    And repeat…

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  235. Data Race Issues
    Use alternative takeLatest

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  236. Forking

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  237. function* mainSaga() {
    yield take('REQUEST_USERS');
    yield call(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }
    store.dispatch(requestUsers());
    store.dispatch(logout());

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  238. function* mainSaga() {
    yield take('REQUEST_USERS');
    yield call(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }
    store.dispatch(requestUsers());
    store.dispatch(logout());

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  239. function* mainSaga() {
    yield take('REQUEST_USERS');
    yield call(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }
    store.dispatch(requestUsers());
    store.dispatch(logout());

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  240. function* mainSaga() {
    yield take('REQUEST_USERS');
    yield call(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }
    store.dispatch(requestUsers());
    store.dispatch(logout());

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  241. function* mainSaga() {
    yield take('REQUEST_USERS');
    yield call(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }
    store.dispatch(requestUsers());
    store.dispatch(logout());

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  242. function* mainSaga() {
    yield take('REQUEST_USERS');
    yield call(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }
    store.dispatch(requestUsers());
    store.dispatch(logout());
    Missed

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  243. function* mainSaga() {
    yield take('REQUEST_USERS');
    yield call(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }
    store.dispatch(requestUsers());
    store.dispatch(logout());
    Missed
    Never
    reached

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  244. mainSaga
    yield take(
    'REQUEST_USERS'
    );

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  245. View
    Middleware
    store.dispatch(
    requestUsers()
    );
    mainSaga

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  246. mainSaga
    fetchUsersSaga
    call

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  247. mainSaga
    fetchUsersSaga
    call
    yield call(
    fetchUsersSaga
    );

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  248. mainSaga
    fetchUsersSaga
    call
    View
    Middleware
    store.dispatch(
    logout()
    );
    ×

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  249. import { fork } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    yield fork(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }

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  250. import { fork } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    yield fork(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }

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  251. import { fork } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    yield fork(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }
    Nonblocking

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  252. import { fork } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    yield fork(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }

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  253. import { fork } from 'redux-saga/effects';
    function* fetchUsersSaga() {
    yield take('REQUEST_USERS');
    const response = yield call(axios.get, '/users');
    yield put(receiveUsers(response.data));
    }
    function* mainSaga() {
    yield fork(fetchUsersSaga);
    yield take('LOGOUT');
    yield call(logoutSaga);
    }
    Won’t miss now

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  254. mainSaga

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  255. mainSaga
    fetchUsersSaga
    fork
    yield fork(
    fetchUsersSaga
    );

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  256. View
    Middleware
    store.dispatch(
    requestUsers()
    );
    mainSaga
    fetchUsersSaga

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  257. mainSaga
    fetchUsersSaga
    yield call(
    axios.get,
    '/users'
    );

    View Slide

  258. mainSaga
    fetchUsersSaga
    yield take(
    'LOGOUT'
    );

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  259. mainSaga
    fetchUsersSaga
    View
    Middleware
    store.dispatch(
    logout()
    );

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  260. Miscellaneous Patterns

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  261. Miscellaneous Patterns
    • Autosaving background tasks

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  262. Miscellaneous Patterns
    • Autosaving background tasks
    • Races for timeouts

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  263. Miscellaneous Patterns
    • Autosaving background tasks
    • Races for timeouts
    • Task cancellation

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  264. Miscellaneous Patterns
    • Autosaving background tasks
    • Races for timeouts
    • Task cancellation
    • Throttling and debouncing

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  265. Miscellaneous Patterns
    • Autosaving background tasks
    • Races for timeouts
    • Task cancellation
    • Throttling and debouncing
    • Hook up to other IO sources

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  266. Resources
    •Redux
    • redux.js.org
    • egghead.io/courses/getting-started-with-redux
    •React
    • github.com/reactjs/react-redux
    •Redux Saga
    • redux-saga.github.io/redux-saga
    • Testing
    • github.com/jfairbank/redux-saga-test-plan

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  267. Thanks!
    Code:
    github.com/jfairbank/state-side-effects-and-redux
    Slides:
    bit.ly/jazzcon-redux
    Jeremy Fairbank
    @elpapapollo / jfairbank

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