Ref Example

class Noti extends React.Component {
  show() {
    console.log("show");
  }
  render() {
    return "eee";
  }
}

export default class App extends React.Component {
  constructor(props) {
    super(props);
    this.notiRef = React.createRef();
  }

  componentDidMount() {
    if (this.notiRef) {
      this.notiRef.show();
    }
  }

  render() {
    return <Noti ref={el => (this.notiRef = el)} />;
  }
}