HMR setup with `react-navigation`

Since we don't know how your project looks like, we will use one of the possible setups. If your project is structured differently, please tweak this guide according to your needs.

---

Let's assume you have index.js file which imports your screens:

// index.js
import {
  AppRegistry,
} from 'react-native';
import { StackNavigator } from 'react-navigation';

import HomeScreen from './src/HomeScreen';
import SecondScreen from './src/SecondScreen';

const MyApp = StackNavigator({
  Home: { screen: HomeScreen },
  Second: { screen: SecondScreen },
});

AppRegistry.registerComponent('MyApp', () => MyApp);

First thing you need to do is to add the following code snipped at the top of App.js file:

// index.js
+ import 'haul/hot/patch';
+ import { makeHot, clearCacheFor, redraw } from 'haul/hot';
import {
  AppRegistry,
} from 'react-native';
import { StackNavigator } from 'react-navigation';

import HomeScreen from './src/HomeScreen';
import SecondScreen from './src/SecondScreen';

const MyApp = StackNavigator({
  Home: { screen: HomeScreen },
  Second: { screen: SecondScreen },
});

AppRegistry.registerComponent('MyApp', () => MyApp);

import 'haul/hot/patch' must be placed before anything else, since the code in that file must be executed at the very beginning!

---

Now, if you're defining your screens using screen property, you must replace it with getScreen and convert the value to a function:

// index.js
import 'haul/hot/patch';
import { makeHot, clearCacheFor, redraw } from 'haul/hot';
import {
  AppRegistry,
} from 'react-native';
import { StackNavigator } from 'react-navigation';

import HomeScreen from './src/HomeScreen';
import SecondScreen from './src/SecondScreen';

const MyApp = StackNavigator({
-   Home: { screen: HomeScreen },
-   Second: { screen: SecondScreen },
+   Home: { getScreen: () => HomeScreen },
+   Second: { getScreen: () => SecondScreen },
});

AppRegistry.registerComponent('MyApp', () => MyApp);

Then, wrap those screen factories with makeHot call and pass the name of the screen as a second argument:

// index.js
import 'haul/hot/patch';
import { makeHot, clearCacheFor, redraw } from 'haul/hot';
import {
  AppRegistry,
} from 'react-native';
import { StackNavigator } from 'react-navigation';

import HomeScreen from './src/HomeScreen';
import SecondScreen from './src/SecondScreen';

const MyApp = StackNavigator({
-   Home: { getScreen: () => HomeScreen },
-   Second: { getScreen: () => SecondScreen },
+   Home: { getScreen: makeHot(() => HomeScreen, 'Home') },
+   Second: { getScreen: makeHot(() => SecondScreen, 'Second') },
});

AppRegistry.registerComponent('MyApp', () => MyApp);

---

Now, the screens can be updated upon hot update by calling redraw. Place the following code snipped at the end of the file:

// index.js
import 'haul/hot/patch';
import { makeHot, clearCacheFor, redraw } from 'haul/hot';
import {
  AppRegistry,
} from 'react-native';
import { StackNavigator } from 'react-navigation';

import HomeScreen from './src/HomeScreen';
import SecondScreen from './src/SecondScreen';

const MyApp = StackNavigator({
  Home: { getScreen: makeHot(() => HomeScreen, 'Home') },
  Second: { getScreen: makeHot(() => SecondScreen, 'Second') },
});

AppRegistry.registerComponent('MyApp', () => MyApp);

+ if (module.hot) {
+   module.hot.accept('./src/HomeScreen.js', () => {
+     clearCacheFor(require.resolve('./src/HomeScreen'));
+     redraw(() => require('./src/HomeScreen').default, 'Home');
+   });
+   module.hot.accept('./src/SecondScreen.js', () => {
+     clearCacheFor(require.resolve('./src/SecondScreen'));
+     redraw(() => require('./src/SecondScreen').default, 'Second');
+   });
+ }

Each screen must have a separate module.hot.accept call with first argument being a path to the file with the screen. Usually you can just copy the path from import statement.

Inside each module.hot.accept's second argument (which is a function), you need to call clearCacheFor with require.resolve and the path to a screen. Finally, you need to call redraw function and pass screen factory method, which must return an updated screen component (the best way to do it, is to require it) and the name of the screen - the same one as in makeHot.

Now, enable HMR from Developer menu by taping Enable Hot Reloading.