React生命周期, 兄弟组件之间通信

1、一个demo（https://www.reactjscn.com/docs/state-and-lifecycle.html）

class Clock extends React.Component {
    constructor(props) {
      super(props);
      this.state = {date: new Date()};
    }

    componentDidMount() {
      this.timerID = setInterval(
        () => this.tick(),
        1000
      );
    }

    componentWillUnmount() {
      clearInterval(this.timerID);
    }

    tick() {
      this.setState({
        date: new Date()
      });
    }

    render() {
      return (
        <div>
          <h1>Hello, world!</h1>
          <h2>It is {this.state.date.toLocaleTimeString()}.</h2>
        </div>
      );
    }
  }

  ReactDOM.render(
    <Clock />,
    document.getElementById('root')
  );

2、demo: 兄弟组件之间通信，使用到生命周期钩子componentWillReceiveProps

项目结构：

demo效果：“搜索组件”传递keyword参数给父组件，然后父组件将keyword参数传递给“显示子组件”

App.jsx

import React from 'react'
import UserSearch from '../user-search/UserSearch.jsx'
import UserList from '../user-list/UserList.jsx'

export default class App extends React.Component {
    constructor(props) {
        super(props)
        this.state = {
            keyword: ''
        }

        this.setKeyword = this.setKeyword.bind(this)
    }

    setKeyword(keyword) {
        console.log(`App组件setKeyword被调用, keyword=${keyword}`)
        this.setState({ keyword })
    }

    render() {
        return (
            <div>
                <UserSearch setKeyword={this.setKeyword} />
                <UserList keyword={this.state.keyword} />
            </div>
        )
    }
}

　　

　　UserSearch.jsx

import React from 'react'
import PropTypes from 'prop-types'

export default class UserSearch extends React.Component {
    state = {
        keyword: ''
    }

    static propTypes = {
        setKeyword: PropTypes.func.isRequired
    }

    render() {
        const { keyword} = this.state
        return (
            <div>
                <h3>搜索用户</h3>
                <input type="text" placeholder="请输入搜索关键字" name="keyword" value={keyword} onChange={(e) => this.keywordInputOnChangeHandler(e)} />
                <input type="button" value="开始搜索" onClick={() => this.searchClickHandler()} />
            </div>
        )
    }

    keywordInputOnChangeHandler = (e) => {
        const keyword = e.target.value
        this.setState({ keyword })
    }

    searchClickHandler = () => {
        const { keyword } = this.state
        console.log(`keyword.trim()=${keyword.trim()}`)
        if (!keyword.trim()) return
        this.props.setKeyword(keyword)
    }
}

　　UserList.jsx

import React from 'react'
import PropTypes from 'prop-types'
import Axios from 'axios'

export default class UserList extends React.Component {
    state = {
        userList: []
    }

    componentWillReceiveProps(newProps) {
        const { keyword } = newProps
        Axios.get(`http://localhost:4000/react-db-crud/user/search?keyword=${keyword}`)
            .then(res => {
                if (res.data.code == 0) {
                    const userList = res.data.data
                    console.log(`userList=${JSON.stringify(userList)}`)
                    this.setState({ userList })
                }
            })
    }

    render() {
        return (
            <div>
                {
                    this.state.userList.map(user => <p>{user.id + "--" + user.name + "--" + user.age}</p>)
                }
            </div>
        )
    }
}

UserList.propTypes = {
    keyword: PropTypes.string.isRequired
}