old_contents: import React from 'react';
  import {StateNavigator} from 'navigation';
  import {NavigationHandler} from 'navigation-react';
  import {NavigationStack, TabBarIOS, TabBarItemIOS} from 'navigation-react-native';
  import Home from './Home';
  import Notifications from './Notifications';
  import Tweet from './Tweet';
  import Timeline from './Timeline';
  import {getHome, getFollows, getTweet, getTimeline} from './data';
  
  var stateNavigator = new StateNavigator([
    {key: 'home', title: 'Home'},
    {key: 'notifications', title: 'Notifications'},
    {key: 'tweet', title: 'Tweet', trackCrumbTrail: true},
    {key: 'timeline', title: 'Timeline', trackCrumbTrail: true}
  ]);
  const {home, notifications, tweet, timeline} = stateNavigator.states;
  home.renderScene = () => <Home tweets={getHome()} follows={getFollows()} />;
  notifications.renderScene = () => <Notifications follows={getFollows()} />;
  tweet.renderScene = ({id}) => <Tweet tweet={getTweet(id)}  />;
  timeline.renderScene = ({id}) => <Timeline timeline={getTimeline(id)}  />;
  
  timeline.getTitle = ({sceneTitle}) => sceneTitle;
  
  var notificationsNavigator = new StateNavigator(stateNavigator);
  stateNavigator.navigate('home');
  notificationsNavigator.navigate('notifications');
  
  export default () => (
    <TabBarIOS style={{flex: 1}}>
      <NavigationHandler stateNavigator={stateNavigator}>
        <NavigationStack
          crumbStyle={from => from ? 'scale_in' : 'scale_out'}
          unmountStyle={from => from ? 'scale_in' : 'scale_out'}>
          <TabBarItemIOS title="Home" />
        </NavigationStack>
      </NavigationHandler>
      <NavigationHandler stateNavigator={notificationsNavigator}>
        <NavigationStack
          crumbStyle={from => from ? 'scale_in' : 'scale_out'}
          unmountStyle={from => from ? 'scale_in' : 'scale_out'}>
          <TabBarItemIOS title="Notifications" />
        </NavigationStack>
      </NavigationHandler>
    </TabBarIOS>
  );
  
new_contents: import React from 'react';
  import {StateNavigator} from 'navigation';
  import {NavigationHandler} from 'navigation-react';
  import {NavigationStack, TabBarIOS, TabBarItemIOS} from 'navigation-react-native';
  import Home from './Home';
  import Notifications from './Notifications';
  import Tweet from './Tweet';
  import Timeline from './Timeline';
  import {getHome, getFollows, getTweet, getTimeline} from './data';
  
  var stateNavigator = new StateNavigator([
    {key: 'home', title: 'Home'},
    {key: 'notifications', title: 'Notifications'},
    {key: 'tweet', title: 'Tweet', trackCrumbTrail: true},
    {key: 'timeline', title: 'Timeline', trackCrumbTrail: true}
  ]);
  const {home, notifications, tweet, timeline} = stateNavigator.states;
  home.renderScene = () => <Home tweets={getHome()} follows={getFollows()} />;
  notifications.renderScene = () => <Notifications follows={getFollows()} />;
  tweet.renderScene = ({id}) => <Tweet tweet={getTweet(id)}  />;
  timeline.renderScene = ({id}) => <Timeline timeline={getTimeline(id)}  />;
  
  timeline.getTitle = ({sceneTitle}) => sceneTitle;
  
  var notificationsNavigator = new StateNavigator(stateNavigator);
  stateNavigator.navigate('home');
  notificationsNavigator.navigate('notifications');
  
  export default () => (
    <TabBarIOS style={{flex: 1}}>
      <NavigationHandler stateNavigator={stateNavigator}>
        <NavigationStack
          title={({getTitle, title}, data) => getTitle ? getTitle(data) : title}
          crumbStyle={from => from ? 'scale_in' : 'scale_out'}
          unmountStyle={from => from ? 'scale_in' : 'scale_out'}>
          <TabBarItemIOS title="Home" />
        </NavigationStack>
      </NavigationHandler>
      <NavigationHandler stateNavigator={notificationsNavigator}>
        <NavigationStack
          title={({getTitle, title}, data) => getTitle ? getTitle(data) : title}
          crumbStyle={from => from ? 'scale_in' : 'scale_out'}
          unmountStyle={from => from ? 'scale_in' : 'scale_out'}>
          <TabBarItemIOS title="Notifications" />
        </NavigationStack>
      </NavigationHandler>
    </TabBarIOS>
  );
  
subject: Set dynamic screen titles