This is a simple demo of how to get Rails and Webpack configured for React Hot Module Replacement (HMR) and setup Guard + LiveReload for live CSS updates.
Hot Module Replacement exchanges, adds, or removes modules while an application is running without a page reload. This is really nice for development as it rerenders your component hierarchy whenever a file is changed, but maintains app state (no need to refresh and navigate back to where you were).
The following steps are needed to setup HMR for development:
- Add
webpack-dev-serverandreact-hot-loader(> v 3.0) as npm dev dependencies.
npm install --save-dev webpack-dev-server [email protected]
- Add hot-loader and devServer settings to
webpack.config.js.
// webpack.config.js
var path = require("path")
var webpack = require("webpack")
module.exports = {
context: __dirname,
// each is loaded as a module
entry: [
'react-hot-loader/patch', // hmr module
'webpack-dev-server/client?http://0.0.0.0:8080', // webpack-dev-server module
'webpack/hot/only-dev-server', // webpack-dev-server hot reloading module
path.join(__dirname, 'frontend', 'index.jsx') // our frontend code module
],
output: {
filename: 'bundle.js',
path: path.resolve(__dirname, 'app', 'assets', 'javascripts')
},
module: {
loaders: [{
test: [/\.jsx?$/],
exclude: /node_modules/,
// make sure 'react-hot-loader/webpack' goes first as these are loaded in order
loaders: ['react-hot-loader/webpack', 'babel-loader'],
}]
},
plugins: [
new webpack.HotModuleReplacementPlugin(),
new webpack.NamedModulesPlugin(),
],
devtool: 'source-maps',
resolve: {
extensions: [".js", ".jsx", "*"],
},
devServer: {
// specifies that 'module.hot === true'
hot: true,
// serves these files
contentBase: path.resolve(__dirname, 'app', 'assets', 'javascripts'),
// at this path
publicPath: 'http://localhost:8080/javascripts',
// allows localhost to localhost requests
headers: {
"Access-Control-Allow-Origin": "http://localhost:3000",
"Access-Control-Allow-Methods": "GET, POST, PUT, DELETE, PATCH, OPTIONS",
"Access-Control-Allow-Headers": "X-Requested-With, content-type, Authorization",
"Access-Control-Allow-Credentials": "true",
}
}
}- Include React Hot Loader in entry file
// index.jsx
// import AppContainer
import { AppContainer } from 'react-hot-loader'
// define a render method to be called on hot-reload
// make sure to wrap your root component in 'AppContainer'
const render = () =>
ReactDOM.render(<AppContainer><Root /></AppContainer>,
document.getElementById('root'))
// initialize rendering
render()
// give hotloader component to watch and the render callback
if (module.hot) module.hot.accept('./Root', render)- Add
bundle.jsto Rails application layout
<!-- app/views/layouts/application.html.erb -->
<!DOCTYPE html>
<html>
<head>
<title>RailsHmrDemo</title>
<%= csrf_meta_tags %>
<%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track': 'reload' %>
<%= javascript_include_tag 'application', 'data-turbolinks-track': 'reload' %>
<%= javascript_include_tag 'bundle' %>
</head>
<body>
<%= yield %>
</body>
</html>- Add asset host to development environment
# config/environments/development
Rails.application.configure do
# other config ...
# Hot-reloading of bundle files
config.action_controller.asset_host = Proc.new { |source|
if source =~ /bundle\.js$/i
"http://localhost:8080"
end
}
endNow to keep webpack watching and HMR hot-reloading, simply run webpack-dev-server --inline --progress. I recommend adding this as a script to your package.json.
- Add Guard and LiveReload gems to
development
group :development do
# other dev gems...
# live css reloading
gem 'guard-rails', require: false
gem 'guard-livereload', require: false
gem 'rack-livereload'
gem "rb-fsevent", :require => false
end- Initialize
Guardfile
- Run
guard init livereloadto generate a Guardfile. The defaults should work just fine.
Now just run guard exec -P livereload during development to run style injection.