如何在React组件中访问动态生成/呈现的子级？

// 父组件
import React from 'react';
import ChildComponent from './ChildComponent';

class ParentComponent extends React.Component {
  render() {
    return (
      <div>
        <ChildComponent />
      </div>
    );
  }
}

// 子组件
import React from 'react';

class ChildComponent extends React.Component {
  render() {
    return (
      <div>
        子组件内容
      </div>
    );
  }
}

export default ChildComponent;

// 父组件
import React from 'react';

class ParentComponent extends React.Component {
  constructor(props) {
    super(props);
    this.childRef = React.createRef();
  }

  componentDidMount() {
    console.log(this.childRef.current); // 访问子组件
  }

  render() {
    return (
      <div>
        <ChildComponent ref={this.childRef} />
      </div>
    );
  }
}

// 子组件
import React from 'react';

class ChildComponent extends React.Component {
  render() {
    return (
      <div>
        子组件内容
      </div>
    );
  }
}

export default ChildComponent;