const CustomTextInput = React.forwardRef((props, ref) => (
   <input type="text" ref={ref} />));class AutoFocusTextInput extends React.Component {
   constructor(props) {
      super(props);
      this.textInput = React.createRef();
   }
   componentDidMount() {      // accessing method of grandchild component directly
      this.textInput.current.focus();
   }
   render() {
      return (<CustomTextInput ref={this.textInput} />);
   }}ReactDOM.render(<AutoFocusTextInput />, document.querySelector('div'));