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 ?

ReactUpdates.ReactReconcileTransaction.release(transaction);
}
/**
 * As soon as `ReactMount` is refactored to not rely on the DOM, we can share
 * code between the two. For now, we'll hard code the ID logic.
 */
var ReactNativeMount = {
  _instancesByContainerID: {},
  
  findNodeHandle: require('findNodeHandle'),
  /**
   * @param {ReactComponent} instance Instance to render.
   * @param {containerTag} containerView Handle to native view tag
   */
  renderComponent: function(
    nextElement: ReactElement,
    containerTag: number,
    callback?: ?(() => void)
  ): ?ReactComponent<any, any, any> {
    var nextWrappedElement = new ReactElement(
      TopLevelWrapper,
      null,
      null,
      null,
      null,
      null,
      nextElement
    );
    var topRootNodeID = containerTag;
    var prevComponent = ReactNativeMount._instancesByContainerID[topRootNodeID];