React-Navigation AuthFlow with Saga

authSaga.js

import { effects } from 'redux-saga';
import { NavigationActions } from 'react-navigation';
import { redirect } from './action';
import NavigationConfiguration from '../configuration/NavigationConfiguration';
import {
  REDIRECT,
  AUTHENTICATE,
  UNAUTHENTICATE,
} from './constants';

const navConfig = new NavigationConfiguration();
const isAuthenticatedRouteName = navConfig.isAuthenticatedRouteName;
const isUnauthenticatedRouteName = navConfig.isUnauthenticatedRouteName;
const initialAuthenticatedRouteName = navConfig.getInitialAuthenticatedRouteName();
const initialUnauthenticatedRouteName = navConfig.getInitialUnauthenticatedRouteName();

function* redirectFlow() {
  const state = yield effects.select();
  const authenticated = state.auth.authenticated;
  const index = state.nav.index;
  const routeName = state.nav.routes[index].routeName;

  const redirectRoute = (name, childRouteName) => NavigationActions.reset({
    index: 0,
    actions: [
      NavigationActions.navigate({ routeName: name })
    ],
  });

  if (authenticated && !isAuthenticatedRouteName(routeName)) {
    yield effects.put(redirectRoute(initialAuthenticatedRouteName))
  } else if (!authenticated && !isUnauthenticatedRouteName(routeName)) {
    yield effects.put(redirectRoute(initialUnauthenticatedRouteName))
  }
}

function* authenticateFlow() {
  yield effects.put(redirect());
}

function* unauthenticateFlow() {
  yield effects.put(redirect());
}

export default function* root() {
  yield effects.takeLatest(REDIRECT, redirectFlow);
  yield effects.takeLatest(AUTHENTICATE, authenticateFlow);
  yield effects.takeLatest(UNAUTHENTICATE, unauthenticateFlow);
}

Index.js

import React from 'react'
import { connect } from 'react-redux'
import { redirect as redirectAction } from 'src/redux/auth/action';

class Index extends React.Component {

  static propTypes = {
    redirect: React.PropTypes.func.isRequired,
  };

  componentDidMount() {
    this.props.redirect();
  }

  render() {
    return null;
  }
}

export default connect(null, { redirect: () => redirectAction() })(Index);

NavigationConfiguration.js

import React from 'react';
import { addNavigationHelpers, StackNavigator } from 'react-navigation';
import { connect } from 'react-redux';
import { styles } from '../../components/Container'

import Index from '../../containers/Index';
import Home from '../../containers/Home';
import Login from '../../containers/Login';

const NAV_ID = 'nav';
const INITIAL_AUTHENTICATED_ROUTE_NAME = 'Home';
const INITIAL_UNAUTHENTICATED_ROUTE_NAME = 'Login';

const AUTHENTICATED_ROUTES = {
  Home: { screen: Home },
};
const UNAUTHENTICATED_ROUTES = {
  Login: { screen: Login },
};

const AppNavigator = StackNavigator({
  Index: { screen: Index, },
  ...AUTHENTICATED_ROUTES,
  ...UNAUTHENTICATED_ROUTES,
}, {
  initialRouteName: 'Index',
});

const ConnectedAppNavigator = connect(state => ({ [NAV_ID]: state[NAV_ID] }))(props => (
  <AppNavigator style={styles.typeFill} navigation={addNavigationHelpers({
    dispatch: props.dispatch,
    state: props[NAV_ID]
  })}/>
));

export default class NavigationConfiguration {

  getAppNavigator() {
    return ConnectedAppNavigator;
  }

  isAuthenticatedRouteName(routeName) {
    return !!AUTHENTICATED_ROUTES[routeName];
  }

  isUnauthenticatedRouteName(routeName) {
    return !!UNAUTHENTICATED_ROUTES[routeName];
  }

  getInitialAuthenticatedRouteName(){
    return INITIAL_AUTHENTICATED_ROUTE_NAME;
  }

  getInitialUnauthenticatedRouteName(){
    return INITIAL_UNAUTHENTICATED_ROUTE_NAME;
  }

  getReducerId() {
    return NAV_ID;
  }

  getReducer() {
    return {
      [NAV_ID]: (state, action) =>
      AppNavigator.router.getStateForAction(action, state) || state,
    }
  }
}

Good idea indeed!
Ref: react-navigation/react-navigation#395 (comment)