如何让react子节点在子节点不受我控制时进行渲染

class ParentComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      showChild: true // 控制是否渲染子节点
    };
  }

  render() {
    return (
      <div>
        {this.state.showChild && <ChildComponent />}
      </div>
    );
  }
}

class ParentComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      showChild: false // 控制是否渲染子节点
    };
  }

  componentDidMount() {
    this.setState({ showChild: true });
  }

  render() {
    return (
      <div>
        {this.state.showChild && <ChildComponent />}
      </div>
    );
  }
}

class ParentComponent extends React.Component {
  render() {
    return (
      <div>
        {React.Children.map(this.props.children, child => child)}
      </div>
    );
  }
}