title: How to get ref from a React 16 portal?
body: <p>Is there a way to get <code>ref</code> from a React 16 portal. I tried the following approach but it doesn't seem to work:</p>
  
  <pre><code>const Tooltip = props =&gt; (
    ReactDOM.createPortal(
      &lt;div&gt;{props.children}&lt;/div&gt;,
      // A DOM element
      document.body
    )
  );
  
  class Info extends React.Component {
     render() {
        return (
          &lt;Tooltip 
            ref={ el =&gt; this.tooltip = el }
          &gt;
            My content
          &lt;/Tooltip&gt;
        ); 
     }
  
     componentDidMount() {
        console.log(this.tooltip); // undefined
     }
  }
  </code></pre>
  
  <p>I need the <code>ref</code> in order to dynamically calculate the element final position!</p>
  
  <p><a href="https://codepen.io/anon/pen/QqmBpB" rel="noreferrer">https://codepen.io/anon/pen/QqmBpB</a></p>