React如何在父组件中使用子组件

class ParentComponent extends React.Component {
  render() {
    const data = "Hello, World!";
    return <ChildComponent data={data} />;
  }
}

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

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

  handleClick() {
    this.childRef.current.method();
  }

  render() {
    return (
      <div>
        <ChildComponent ref={this.childRef} />
        <button onClick={() => this.handleClick()}>Call Child Method</button>
      </div>
    );
  }
}

class ChildComponent extends React.Component {
  method() {
    console.log("Child method called");
  }

  render() {
    return <div>Child Component</div>;
  }
}