我的第一个 react redux demo
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互联网集市收集整理的这篇技术教程文章主要介绍了我的第一个 react redux demo，小编现在分享给大家，供广大互联网技能从业者学习和参考。文章包含10828字，纯文字阅读大概需要16分钟。
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最近学习react redux，先前看过了几本书和一些博客之类的，感觉还不错，比如《深入浅出react和redux》,《React全栈++Redux+Flux+webpack+Babel整合开发》，《React与Redux开发实例精解》， 个人觉得《深入浅出react和redux》这本说讲的面比较全， 但是 很多都是蜻蜓点水， 不怎么深入。这里简单记录一个redux 的demo， 主要方便以后自己查看，首先运行界面如下：
项目结构如下：
这里我们一共有2个组件，都在components文件夹下面，Picker.js实现如下：
import React from‘react‘; import PropTypes from‘prop-types‘; function Picker({value, onChange, options}) { return( <span> <h1>{value}</h1> <select onChange={e=>onChange(e.target.value)} value={value}> {options.map(o=> <option value={o} key={o}>{o}</option> )} </select> </span> ); } Picker.propTypes = { options:PropTypes.arrayOf(PropTypes.string.isRequired).isRequired, value:PropTypes.string.isRequired, onChange:PropTypes.func.isRequired, }; export default Picker;这里的onChange事件是传递进来的，最终就是要触发一个action，Posts.js的实现如下：
import React from‘react‘; import PropTypes from‘prop-types‘; function Posts ({posts}){ return( <ul> { posts.map((p,i)=> <li key={i}>{p.title}</li> ) } </ul> ); } Posts.propTypes = { posts:PropTypes.array.isRequired, }; export default Posts;
-
现在来看看actions/index.js的实现：
import fetch from‘isomorphic-fetch‘; export const REQUEST_POSTS = ‘REQUEST_POSTS‘; export const RECEIVE_POSTS = ‘RECEIVE_POSTS‘; export const SELECT_REDDIT = ‘SELECT_REDDIT‘; export const INVALIDATE_REDDIT = ‘INVALIDATE_REDDIT‘; export function selectReddit(reddit){ return{ type:SELECT_REDDIT, reddit, }; } export function invalidateReddit(reddit){ return { type:INVALIDATE_REDDIT, reddit, }; } export function requestPosts(reddit){ return { type:REQUEST_POSTS, reddit, }; } export function receivePosts(reddit,json){ return{ type:RECEIVE_POSTS, reddit, posts:json.data.children.map(x=>x.data), receivedAt:Date.now(), }; } function fetchPosts(reddit){ return dispatch=>{ dispatch(requestPosts); return fetch(`https://www.reddit.com/r/${reddit}.json`) .then(r=>r.json()) .then(j=>dispatch(receivePosts(reddit,j))); } } function shouldFetchPosts(state,reddit){ const posts = state.postsByReddit[reddit]; if(!posts){ returntrue; } if(posts.isFetching){ returnfalse; } return posts.didInvalidate; } export function fetchPostsIfNeeded(reddit){ return (dispatch,getState)=>{ if(shouldFetchPosts(getState(),reddit)){ return dispatch(fetchPosts(reddit)); } returnnull; }; }
主要是暴露出selectReddit，invalidateReddit，requestPosts，receivePosts和fetchPostsIfNeeded几个action，而fetchPostsIfNeeded才是主要的，首先调用shouldFetchPosts方法来检查是否需要获取数据， 如果是的话就调用fetchPosts方法，而fetchPosts方法返回的是一个function，这里我的项目使用了redux-thunk， 看看redux-thunk的实现如下：
function createThunkMiddleware(extraArgument) {
return ({ dispatch, getState }) => next => action => {
if (typeof action === ‘function‘) {
return action(dispatch, getState, extraArgument);
}
return next(action);
};
}
const thunk = createThunkMiddleware();
thunk.withExtraArgument = createThunkMiddleware;
export default thunk;
所以在fetchPostsIfNeeded中的dispatch(fetchPosts(reddit)) 最终会进入到redux-thunk里面，fetchPosts(reddit)返回的是一个function如下，所以这里会进入这个action里面，也就是 return action(dispatch, getState, extraArgument);
function fetchPosts(reddit){
return dispatch=>{
dispatch(requestPosts);
return fetch(`https://www.reddit.com/r/${reddit}.json`)
.then(r=>r.json())
.then(j=>dispatch(receivePosts(reddit,j)));
}
}
所以在fetchPosts里面的dispatch参数就是redux-thunk里面return action(dispatch, getState, extraArgument) 的dispatch。
在这里的function里面， 一般发起http请求前有一个 状态改变（dispatch(requestPosts);）， http请求成功后有一个 状态改变（dispatch(receivePosts(reddit,j))），失败也会有状态改变（这里忽律失败的case）
接下来看看containers\App.js
import React, { Component } from‘react‘;
import PropTypes from‘prop-types‘;
import { connect } from‘react-redux‘;
import { selectReddit, fetchPostsIfNeeded, invalidateReddit } from‘../actions‘;
import Picker from‘../components/Picker‘;
import Posts from‘../components/Posts‘;
class App extends Component{
constructor(props){
super(props);
this.handleChange=this.handleChange.bind(this);
this.handleRefreshClick=this.handleRefreshClick.bind(this);
}
componentDidMount(){
console.log(‘执行componentDidMount‘);
const { dispatch, selectedReddit } = this.props;
dispatch(fetchPostsIfNeeded(selectedReddit));
}
componentWillReceiveProps(nextProps){
console.log(‘执行componentWillReceiveProps‘, nextProps);
if(nextProps.selectedReddit !==this.props.selectedReddit)
{
const { dispatch, selectedReddit } = this.props;
dispatch(fetchPostsIfNeeded(selectedReddit));
}
}
handleChange(nextReddit){
this.props.dispatch(selectReddit(nextReddit));
}
handleRefreshClick(e){
e.preventDefault();
const {dispatch, selectedReddit } = this.props;
dispatch(invalidateReddit(selectedReddit));
dispatch(fetchPostsIfNeeded(selectedReddit));
}
render(){
const { selectedReddit, posts, isFetching, lastUpdated } = this.props;
const isEmpty = posts.length === 0;
const message = isFetching ? <h2>Loading...</h2> : <h2>Empty.</h2>;
return(
<div>
<Picker value={selectedReddit} onChange={this.handleChange} options={[‘reactjs‘, ‘frontend‘]} />
<p>
{ lastUpdated && <span>Last updated at {new Date(lastUpdated).toLocaleDateString()}.</span>}
{!isFetching && <a href="#" onClick={this.handleRefreshClick}>Refresh</a>}
</p>
{isEmpty?message:<div style={{opacity:isFetching?0.5:1}}><Posts posts={posts}/></div>}
</div>
);
}
}
App.propTypes = {
selectedReddit:PropTypes.string.isRequired,
posts:PropTypes.array.isRequired,
isFetching:PropTypes.bool.isRequired,
lastUpdated:PropTypes.number,
dispatch:PropTypes.func.isRequired
};
function mapStateToProps(state){
const { selectedReddit, postsByReddit } = state;
const { isFetching, lastUpdated, items: posts,} = postsByReddit[selectedReddit] || { isFetching: true, items: [], };
return {
selectedReddit,
posts,
isFetching,
lastUpdated,
};
}
export default connect(mapStateToProps)(App);
只是要注意一下componentDidMount方法里面是调用dispatch(fetchPostsIfNeeded(selectedReddit));的，页面加载后就发送默认的http请求。
在来看看reducers\index.js:
import {combineReducers} from‘redux‘;
import {SELECT_REDDIT,INVALIDATE_REDDIT,REQUEST_POSTS,RECEIVE_POSTS} from‘../actions‘;
function selectedReddit (state=‘reactjs‘,action) {
switch(action.type){
case SELECT_REDDIT:
return action.reddit;
default:
return state === undefined ? "" : state;
}
}
function posts(state= { isFetching: false, didInvalidate: false,items: [],}, action){
switch(action.type){
case INVALIDATE_REDDIT:
return Object.assign({},state,{didInvalidate:true});
case REQUEST_POSTS:
return Object.assign({},state,{isFetching:true,didInvalidate:false});
case RECEIVE_POSTS:
return Object.assign({},state,{isFetching:false,didInvalidate:false,items:action.posts,lastUpdated:action.receivedAt});
default:
return state;
}
}
function postsByReddit(state={},action){
switch(action.type){
case INVALIDATE_REDDIT:
case RECEIVE_POSTS:
case REQUEST_POSTS:
return Object.assign({},state,{[action.reddit]:posts(state[action.reddit],action)});
default:
return state === undefined ? {} : state;
}
}
const rootReducer =combineReducers({postsByReddit,selectedReddit});
export default rootReducer;
这里用combineReducers来合并了postsByReddit和selectedReddit两个Reducers，所以每个action都会进入这2个Reducers（也不知道我的理解是否正确），比如action type 是INVALIDATE_REDDIT，selectedReddit 什么都不处理，直接返回state，然而postsByReddit会返回我们需要的state。 还有就是经过combineReducers合并后的数据，原先postsByReddit需要的state现在就只能通过state.postsByReddit来获取了。
还有大家主要到了没有， 这里有return state === undefined ? "" : state; 这样的写法， 那是combineReducers在初始化的时候会传递undefined ，combineReducers->assertReducerShape的实现如下：
所以默认的state传递的是undefined，而我们的reducer也是没有处理ActionTypes.INIT的
现在来看看store/configureStore.js
import {createStore,applyMiddleware,compose} from‘redux‘;
import thunkMiddleware from‘redux-thunk‘;
import logger from‘redux-logger‘;
import rootReducer from‘../reducers‘;
const store=createStore(rootReducer,initialState,compose(
applyMiddleware(thunkMiddleware,logger),
window.devToolsExtension? window.devToolsExtension():f=>f
));
if(module.hot){
module.hot.accept(‘../reducers‘,()=>{
const nextRootReducer=require(‘../reducers‘).default;
store.replaceReducer(nextRootReducer);
});
}
return store;
}
module.hot实在启用了热跟新后才可以访问的。
index.js实现：
import ‘babel-polyfill‘; import React from‘react‘; import {render} from‘react-dom‘; import {Provider} from‘react-redux‘; import App from‘./containers/App‘; import configureStore from‘./store/configureStore‘; const store=configureStore(); render( <Provider store={store}> <App /> </Provider> ,document.getElementById(‘root‘) );
server.js实现：
var webpack = require(‘webpack‘);
var webpackDevMiddleware = require(‘webpack-dev-middleware‘);
var webpackHotMiddleware = require(‘webpack-hot-middleware‘);
var config = require(‘./webpack.config‘);
var app= new (require(‘express‘))();
var port= 3000;
var compiler = webpack(config);
app.use(webpackDevMiddleware(compiler, {noInfo:true, publicPath:config.output.publicPath}));
app.use(webpackHotMiddleware(compiler));
app.get("/",function(req,res){
res.sendFile(__dirname+‘/index.html‘);
});
app.listen(port,function(error){
if(error){
console.error(error);
}
else{
console.info("==> ?? Listening on port %s. Open up http://localhost:%s/ in your browser.", port, port)
}
});
package.json文件如下：
{
"
name
": "react-demo",
"version": "1.0.0",
"main": "index.js",
"scripts": {
"start":"node server.js"
},
"keywords": [],
"author": "",
"license": "ISC",
"devDependencies": {
"babel-core": "^6.26.3",
"babel-loader": "^7.1.5",
"babel-preset-es2015": "^6.24.1",
"babel-preset-react": "^6.24.1",
"babel-preset-react-hmre": "^1.1.1",
"expect": "^23.6.0",
"express": "^4.16.3",
"node-libs-browser": "^2.1.0",
"webpack": "^4.20.2",
"webpack-dev-middleware": "^3.4.0",
"webpack-hot-middleware": "^2.24.2"
},
"dependencies": {
"babel-polyfill": "^6.26.0",
"isomorphic-fetch": "^2.2.1",
"react": "^16.5.2",
"react-dom": "^16.5.2",
"react-redux": "^5.0.7",
"redux": "^4.0.0",
"redux-logger": "^3.0.6",
"redux-thunk": "^2.3.0"
}
}
webpack.config.js：
var path = require("path");
var webpack= require(‘webpack‘);
module.exports = {
devtool:‘cheap-module-eval-source-map‘,
entry: [‘webpack-hot-middleware/client‘,‘./index.js‘],
output : {
path:path.join(__dirname,‘dist‘),
filename:"bundle.js",
publicPath:‘/static/‘
},
module:{
rules:[
{
test:/\.js$/,
loaders:[‘babel-loader‘] ,
exclude:‘/node_modules/‘,
include:__dirname
}
]
},
plugins:[
new webpack.optimize.OccurrenceOrderPlugin(),
new webpack.HotModuleReplacementPlugin()
]
}
index.html：
<!DOCTYPE html>
<html>
<head>
<title>Redux async example</title>
</head>
<body>
<div id="root">
</div>
<script src="/static/bundle.js"></script>
</body>
</html>
.babelrc：
{
"
presets
"
: [
"
es2015
","react"
],
"env":{
"development":{
"presets":["react-hmre"]
}
}
}
原文：https://www.cnblogs.com/majiang/p/9744736.html
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