消息订阅与发布技术

安装第三方库

npm install pubsub-js

使用时导入库

import PubSub from 'pubsub-js';

例子：

　　订阅

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('atguigu',(_,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 href={userObj.html_url} rel="noreferrer">
                                    <img alt='head_portrait' src={userObj.avatar_url} style={{width: '100px'}}/>
                                </a>
                                <p className="card-text">{userObj.login}</p>
                            </div>
                        )
                    })
                }
            </div>
        );
    }
}

　　发布

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

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('atguigu',{isFirst:false,isLoading:true})
        //发送网络请求
        axios.get(`http://localhost:3000/api1/search/users?q=${keyword}`).then(
            response =>{
                //请求成功后通知List更新状态
                PubSub.publish('atguigu',{isLoading:false,users:response.data.items})
            },
            error =>{
                //请求失败后通知List更新状态
                PubSub.publish('atguigu',{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>
        );
    }
}