React---消息订阅发布机制

一、PubSubJS的使用

1. 工具库: PubSubJS
2. 下载: npm install pubsub-js --save
3. 使用:

1) import PubSub from 'pubsub-js' //引入

2) PubSub.subscribe('delete', function(data){ }); //订阅

3) PubSub.publish('delete', data) //发布消息

二、案例

接上一篇github搜索案例改造

1. App.jsx

import React, { Component } from 'react'
import Search from './components/Search'
import List from './components/List'

export default class App extends Component {
    render() {
        return (
            <div className="container">
                <Search/>
                <List/>
            </div>
        )
    }
}

2. Search.jsx

import React, { Component } from 'react'
import PubSub from 'pubsub-js'
import axios from 'axios'

export default class Search extends Component {

    search = ()=>{
        //获取用户的输入(连续解构赋值+重命名)
        const {keyWordElement:{value:keyWord}} = this
        //发送请求前通知List更新状态
        PubSub.publish('msg',{isFirst:false,isLoading:true})
        //发送网络请求
        axios.get(`/api1/search/users?q=${keyWord}`).then(
            response => {
                //请求成功后通知List更新状态
                PubSub.publish('msg',{isLoading:false,users:response.data.items})
            },
            error => {
                //请求失败后通知App更新状态
                PubSub.publish('msg',{isLoading:false,err:error.message})
            }
        )
    }

    render() {
        return (
            <section className="jumbotron">
                <h3 className="jumbotron-heading">搜索github用户</h3>
                <div>
                    <input ref={c => this.keyWordElement = c} type="text" placeholder="输入关键词点击搜索"/>&nbsp;
                    <button onClick={this.search}>搜索</button>
                </div>
            </section>
        )
    }
}

3. List.jsx

import React, { Component } from 'react'
import PubSub from 'pubsub-js'
import './index.css'

export default class List extends Component {

    state = { //初始化状态
        users:[], //users初始值为数组
        isFirst:true, //是否为第一次打开页面
        isLoading:false,//标识是否处于加载中
        err:'',//存储请求相关的错误信息
    } 

    componentDidMount(){
        this.token = PubSub.subscribe('msg',(_,stateObj)=>{
            this.setState(stateObj)
        })
    }

    componentWillUnmount(){
        PubSub.unsubscribe(this.token)
    }

    render() {
        const {users,isFirst,isLoading,err} = this.state
        return (
            <div className="row">
                {
                    isFirst ? <h2>欢迎使用，输入关键字，随后点击搜索</h2> :
                    isLoading ? <h2>Loading......</h2> :
                    err ? <h2 style={{color:'red'}}>{err}</h2> :
                    users.map((userObj)=>{
                        return (
                            <div key={userObj.id} className="card">
                                <a rel="noreferrer" href={userObj.html_url} target="_blank">
                                    <img alt="head_portrait" src={userObj.avatar_url} style={{'100px'}}/>
                                </a>
                                <p className="card-text">{userObj.login}</p>
                            </div>
                        )
                    })
                }
            </div>
        )
    }
}

三、扩展Fetch

1. 文档

1. https://github.github.io/fetch/
2. https://segmentfault.com/a/1190000003810652

2. 特点

1. fetch: 原生函数，不再使用XmlHttpRequest对象提交ajax请求
2. 老版本浏览器可能不支持

3. 相关API

1) GET请求

fetch(url).then(function(response) {
    return response.json()
  }).then(function(data) {
    console.log(data)
  }).catch(function(e) {
    console.log(e)
  });

1) POST请求

fetch(url, {
    method: "POST",
    body: JSON.stringify(data),
  }).then(function(data) {
    console.log(data)
  }).catch(function(e) {
    console.log(e)
  })