Let's Redux!

For people who use React but haven’t tried Redux.
- Why - Common issues while people use React
- Redux Basic Concept

Transcript

1. Let’s Redux for people who use React but haven’t tried Redux @josephj6802
2. React.js is Awesome Building a complicate UI was never so easy Plugins Dashboard Widget Composer ACL Term Languages
3. Building a complicate UI was never so easy React.js is Awesome • Easy to learn • Manage State instead of DOM • One-way Data Flow Model • UI = fn(State) Advantages Absolutely a correct technical decision
4. PROBLEMS!! React doesn’t We don’t have a front-end application architecture. “It worked well with simple components, but as our interfaces become more complicate we soon found…”
5. Code Smells • Delegation is difficult • Top-down props • Mixed concerns • View logic • Data fetching • Data decoration • Poor state management • Component-specific • Mutable • Not maintainable <WidgetsEdit/> Top-level Component 1469 lines in total!!
6. React.js = “Good” Parent class WidgetsEdit extends Component { constructor(props) { super(props); } componentWillMount() { $.ajax(...).then((...) => { // ... decorate data ... this.setState(...) }); } render() { let manyStates = that.state; // ... view logic ... return ( <ButtonNavList {...manyStates}> <ButtonNavItem {...manyStates}/> </ButtonNavList> <StylePreview {...manyStates}/> <CodeEditor {...manyStates}/> ) } } who takes care of everything for childs Preparing data, passing props, handling events for childs
7. 22 Event Handlers Child passes all events to its parent because only the top-level component should access state Handling Children Events
8. Delegation or Not? If your think NO, plz put inside… • Pass all <ButtonNavItem/> required props to <ButtonNavList/> • Handle its events in <ButtonNavList/> • Handle its events in <WidgetsEdit/> If your think YES, plz keep there… Handle child logic in top-level component. Both ways are not good… Not Convenient Dirty! Should <ButtonNavItem/> appear in top-level as illustrated?
9. Fetching Data for Childs No Separation of Concerns
10. Why Redux? Not have children? https://github.com/reactjs/redux/issues/151#issuecomment-173749456
11. Why Redux? Solve all the mentioned issues • Delegation is difficult easier • Top-down props including events is not required • Mixed Separation of concerns • View logic • Data fetching goes to ”Action” • Data decoration goes to “Reducer” • Poor Better state management • Component App-specific • Mutable Immutable • Not Maintainable
12. Basic Concept 1. Action 2. Reducer 3. State https://github.com/reactjs/redux/issues/151#issuecomment-134713785
13. 1. Action Pure Object { type: 'SORT_PLUGINS', by: 'id', direction: 'desc' } Minimum data which describes the change Only the “type” property is required
14. 1. Action
15. 1-1. Action Creator Pure function which creates an action function sortPlugins(by, direction = 'desc') { return { type: 'SORT_PLUGINS', by, direction }; } Reusable, Portable, and Easy to Test (Return promise for asynchronous action) Make it easier to create an action
16. 2. Reducer Pure function which returns the next state function reducer(state = {}, action) { switch (action.type) { case 'SORT_PLUGINS': return { ...state, plugins: { orderBy: action.by, orderByDirection: action.direction, data: _.sortByOrder(state.data, action.by, 
 action.direction) } }; default: return state; }; } reducer(previousState, action) => state Initial State Always return current state
17. 2. Reducer reducer(prevState, action) => nextState
18. 3. Store A plain object which holds application state { plugins: { data: [ {id: 1, name: 'AdRoll'}, {id: 2, name: 'Agile CRM'}, {id: 3, name: 'Brand Networks'} ], orderBy: 'id', orderByDirection: 'desc' } } Dispatching actions is the only way to update store Store is the only one state for the whole app
19. 3. Store
20. 3-1. Store Creation with Reducer (the spec of your store) store = createStore(reducer); import {createStore} from 'redux'; let store = createStore(reducer); The store provides several useful API methods
21. store.dispatch(sortPlugins('name', 'desc')); 3-2. Store APIs store#dispatch store#subscribe let currentValue; store.subscribe(() => { let previousValue = currentValue; currentValue = store.getState(); if (previousValue === currentValue) { return; } // DO SOMETHING... }); store#getState
22. Redux Data Flow Reducer Store Action Action Action store = createStore(reducerFn); store.subscribe(eventHandlerFn); App store.dispatch(actionCreatorFn); reducerFn = (currentState, action) => nextState
23. Redux Data Flow Reducer Store Action Action Action store = createStore(reducerFn); store.subscribe(eventHandlerFn); App store.dispatch(actionCreatorFn); reducerFn = (currentState, action) => nextState That’s it! • Super easy for both code and concept • Pure functions & objects w/o side-effects • Provides a better data flow for JS apps • Not just for React.js apps • jQuery or Node.js? No problem!
24. Redux and React? First, let’s check the list again • Delegation is easier • Top-down props is not required • Separation of concerns • View logic • Data fetching goes to ”Action” • Data decoration goes to “Reducer” • Better state management • App-specific • Immutable • Maintainable • Delegation is easier • Top-down props is not required
25. React.js = “Good” Parent class WidgetsEdit extends Component { constructor(props) { super(props); } componentWillMount() { $.ajax(...).then((...) => { // ... decorate data ... this.setState(...) }); } render() { let manyStates = that.state; // ... decorate state ... return ( <ButtonNavList {...manyStates}> <ButtonNavItem {...manyStates}/> </ButtonNavList> <StylePreview {...manyStates}/> <CodeEditor {...manyStates}/> ) } } who takes care of everything of its child components Preparing data & handling events for child components
26. React + Redux = Bad Parent import React, {Component} from 'react'; import {connect} from 'react-redux'; import {fetchData} from ‘./actions'; class WidgetsEdit extends Component { constructor(props) { super(props); } componentWillMount() { this.props.dispatch(fetchData()); } render() { return ( <ButtonNavList> <ButtonNavItem/> <ButtonNavList> <StylePreview/> <CodeEditor/> ) } } WidgetsEdit = connect(mapStateToProps)(WidgetsEdit); who only cares about himself Delegation = Preparing data and dispatching for itself
27. React.js w/ Redux Child component connects to store by itself import React from 'react'; import {connect} from 'react-redux'; import {modeSwitch} from './actions'; let StylePreview({url, dispatch} = props) => { return ( <a onClick={() => dispatch(modeSwitch('mobile'))}>/> Mobile View </a> <iframe src={url}/> ); } StylePreview = connect((state) => { // map state to props return { url: state.widget.url, } })(StylePreview); … And dispatches actions by itself
28. Summary • Good start to learn functional programming • Add complexity but also add maintenance = worthy • Single Store • Time Travel (e.g. Undo) is possible • No need to access React state API anymore • Not only for React.js
29. Further Reading https://egghead.io/series/getting-started-with-redux egghead.io Very good material for learning Redux!
30. Discussion - Store Structure One Store - Could it possibly fit our application?
31. THANK YOU! Let’s Redux!!