I use `ReactDOM.unstable_renderSubtreeIntoContainer` to render a portal.

``` javascript
class Modal extends React.Component {

componentDidMount() {
    this.node = document.createElement('div');
    document.body.appendChild(this.node);
    this.renderPortal(this.props);
}

componentWillReceiveProps(nextProps) {
    this.renderPortal(nextProps);
}

componentWillUnmount() {
    ReactDOM.unmountComponentAtNode(this.node);
    document.body.removeChild(this.node);
}

renderPortal = (props) => {
    renderSubtreeIntoContainer(this, <ModalPortal {...props} />, this.node);
}

render() {
    return null;
  }
}
```

In my root component:

``` javascript
class App extends React.Component {
    static childContextTypes = {
        highlightColor: React.PropTypes.object
    }

    getChildContext() {
        return {
            highlightColor: this.props.highlightColor
        }
    }

    ...
}
```

The context of root component will be updated and passed to children if  `this.props.highlightColor` is changed. This is right.
I can access the correct context in the `<ModalPortal/>` component in the first render.
And after that the context passed to  `<ModalPortal/>` **does not change any more** when the context of root component changed.
But I can access the correct context in the `<Modal/>`  every render.

what's wrong with my code ?

var internalInstance = ReactInstanceMap.get(publicInstance);
  if (!internalInstance) {
    if (__DEV__) {
      
      
      
      warning(
        !callerName,
        '%s(...): Can only update a mounted or mounting component. ' +
        'This usually means you called %s() on an unmounted component. ' +
        'This is a no-op. Please check the code for the %s component.',
        callerName,
        callerName,
        publicInstance.constructor.displayName
      );
    }
    return null;
  }
  if (__DEV__) {
    warning(
      ReactCurrentOwner.current == null,
      '%s(...): Cannot update during an existing state transition (such as ' +
      'within `render` or another component\'s constructor). Render methods ' +