React + Firebase - Persistent auth

App.js

import React, { Component } from 'react';
import PropTypes from 'prop-types';
import firebase from 'firebase';
import { browserHistory } from 'react-router';
import { routeCodes } from 'routes';

export default class App extends Component {

    static propTypes = {
        children: PropTypes.object.isRequired
    }

    constructor (props) {
        super(props);
        this.state = { user: null };
    }

    componentDidMount () {
        this.setAuthObserver();
    }

    /**
     * @description
     * When AuthObserver invokes user change check if
     * current route can be rendered and invoke redirect if necessary.
     *
     * @param  {Object} props
     * @param  {Object} state
     * @return {Function}
     * @private
     */
    componentWillUpdate (props, state) {
        return !this.isAuthorized(props.children.props.route.protected, state.user) &&
            browserHistory.push(routeCodes.ROOT);
    }

    /**
     * @description
     * Set AuthObserver for firebase user change.
     *
     * @return {Function}
     * @private
     */
    setAuthObserver () {
        return firebase.auth().onAuthStateChanged(user => this.setState({ user }));
    }

    /**
     * @description
     * Check if user is logged in or route is public.
     *
     * @param  {Bool} protectedRoute
     * @param  {Object} user
     * @return {Bool}
     * @private
     */
    isAuthorized (protectedRoute, user) {
        return Boolean(user) || !protectedRoute;
    }

    render () {
        return (
            <section>
                {
                    React.Children.map(this.props.children, (child) =>
                        React.cloneElement(child, { key: child.id })) || null
                }
            </section>
        );
    }
}