React Native and Webpack

React Native Webpack Server is a development server that leverages the Webpack Dev Server and the React Packager to enable building React Native JavaScript bundles with webpack. This allows you to use the existing webpack ecosystem when targeting React Native.

If your project depends on react-native < 0.4.3 you will need to lock down the version of this package to 0.1.x.

Installing

npm install --save-dev react-native-webpack-server

Using

By default React Native will look for an index.ios.js at the root of the project. Delete this file and add an entry in your webpack config:

entry: {
  'index.ios': ['./src/main.js']
}

Start the React Native Webpack Server using the included script. You might want to put this in your package.json.

"scripts": {
  "start": "./node_modules/.bin/react-native-webpack-server start"
}

This will start the server on port 8080. The last step is to change the URL of your application bundle in AppDelegate.m, changing 8081 to 8080:

jsCodeLocation = [NSURL URLWithString:@"http://localhost:8080/index.ios.bundle"];

To run the development server:

npm start

Source Maps

Current solutions for building React Native bundles with Webpack lose source maps. This is because the Webpack bundle is first built and then passed off to the React Packager which constructs the source map by hand. This is done for speed, but it also means you can only use transforms that map lines 1 to 1.

React Native Webpack Server enables source maps by generating the react-native and application bundles separately and then combining their source maps.

Hot Reload

Since this is built on Webpack you can now leverage the growing ecosystem of addons such as React Hot Loader.

To enable hot reload, make sure you first install the react-hot-loader package and then start the server with --hot=1.

You'll also need to configure Webpack. See the Babel+ES6 config for an example.

The examples in this repo use a relative path ../../ to link to react-native-webpack-server. You'll need to replace these with the node.js module path: react-native-webpack-server. The 2 places you will see this are in package.json scripts and webpack.config.js hot loader entry.

NOTE: hot reload currently only works with the web socket executor (hit CMD+D in the simulator) or the WebView executor (CMD+CTRL+Z -> Enable Safari Debugging). If you regurlarly use this feature, you might want to default to the web socket exeuctor in development:

RCTBridge.m:

- (void)setUp
{
  Class executorClass = _executorClass ?: _globalExecutorClass ?: [RCTContextExecutor class];
#if DEBUG
  executorClass = NSClassFromString(@"RCTWebSocketExecutor");
#endif
  ...
  }

Replace RCTWebSocketExecutor with RCTWebViewExecutor if you wish to use the Safari WebKit inspector instead of the Chrome dev tools.

Packaging for release

When you are ready to ship your app, you will want to generate a minified bundle and package it in the binary. You can build a minified bundle using the dev and minify URL parameters. Setting these to false or 0 will tell the React Native packager to minify and remove debug code.

In your webpack config, you will likely want to enable the UglifyJsPlugin. The sample apps are configured to enable minification when process.env.NODE_ENV is set to production. See the BabelES6 webpack config for an example.

To generate and copy the minified bundle into the iOS project:

curl 'http://localhost:8080/index.ios.bundle?dev=false&minify=true' -o iOS/main.jsbundle

You will need to uncomment this line in AppDelegate.m in order to load the local bundle.

FAQ

I can't import 3rd party modules in my project.

Most react-native 3rd party modules are published to npm in ES6+ since the react-native packager handles transpiling. You may need to whitelist these modules in your webpack config, as the default configuration in the example excludes all of node_modules. See issue #34.

I get the red box of death when using hot reload even after fixing the exception.

Your code is still executing. Dismiss the red box using the Esc key.

Why is hot reload using a no-op setInterval() in my app?

It's a terrible hack to jump back onto the React Native runloop when a module is changed. If you have a better idea, please open a PR :)

Source map generation is really slow on io.js.

On a late-2012 Macbook Pro, it takes about 1.5 seconds to generate the source map for react-native on io.js. On stable node (0.12.x) it takes around 200ms. I originally thought this was an issue with source-map but in an isolated test with the entirety of react-native I found io.js and node.js (stable) to be about the same. If you have any ideas, please let me know. In the meantime, it's best to use the latest stable version of node.js.