javascript – 为什么更高阶组件中的componentDidMount被调用多次？

2023年3月1日 440次阅读

docs说：

Invoked once, only on the client (not on the server), immediately
after the initial rendering occurs.

现在,当我尝试创建更高阶的组件时：

import React from 'react';
import { connect } from 'react-redux';

function wrap(Wrapped) {

  class Wrapper extends React.Component {
    componentDidMount() {
      // I will place some reusable functionality here which need to
      // be called once on mounted.
      console.log('wrapper component mounted');
    }
    render() {
      return <Wrapped {...this.props}/>
    }
  }
  return Wrapper;
}

class Wrapped extends React.Component {
  componentDidMount() {
    console.log('wrapped component mounted');
  }
  render() {
    return <div></div>;
  }
}

connect()(wrap(Wrapped));

现在,每次在props中发生任何更改时,控制台都会打印出：

'wrapped component mounted'
'wrapper component mounted'

如果我删除Wrapper,它只打印一次(安装时)
在第一时间)：

`wrapped component mounted`

那么,为什么componentDidMount在更高阶的组件中不止一次被调用？

最佳答案 连接()(包裹物(包装)); < – 用Wrapped替换 我测试了它.它有效.

function wrap(Wrapped) {
  class Wrapper extends React.Component {
    componentDidMount() {
      console.log('wrapper component mounted');
    }
    render() {
      return <Wrapped {...this.props}/>
    }
    componentDidUpdate(prevProps, prevState){
        console.log(this.props);
    }
  }
  return Wrapper;
}
class Wrapped extends React.Component {
  componentDidMount() {
    console.log('wrapped component mounted');
  }
  componentDidUpdate(prevProps, prevState){
      console.log(this.props);
  }
  render() {
    return <div></div>;
  }
}

connect(state=>({state}))(wrap(Wrapped));

wrap func返回Wrapper,你无法将Wrapper传递给wrap func.这是循环

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