# React-Rails v3
[](http://rubygems.org/gems/react-rails)
[](https://www.npmjs.com/package/react_ujs)
[](https://github.com/reactjs/react-rails/actions/workflows/ruby.yml)
## News
V3.0.0 is released with Shakapacker v6 support, including SSR. Please try it out and report any issues. We'll try to address any critical issues ASAP.
For version 2.7 documentation checkout [2.7-stable](https://github.com/reactjs/react-rails/tree/2.7-stable) branch.
## Summary
React-Rails is a flexible tool to use [React](http://facebook.github.io/react/) with Rails. The benefits:
* Automatically renders React server-side and client-side
* Supports [Shakapacker](https://github.com/shakacode/shakapacker) v7
* Supports Sprockets 4.x, 3.x
* Lets you use [JSX](http://facebook.github.io/react/docs/jsx-in-depth.html), [ES6](http://es6-features.org/), [TypeScript](https://www.typescriptlang.org/), [CoffeeScript](http://coffeescript.org/)
---
## ShakaCode Support
[ShakaCode](https://www.shakacode.com) offers support for upgrading this gem, and related gems such as Webpacker and using Shakapacker. If interested, contact Justin Gordon, [justin@shakacode.com](mailto:justin@shakacode.com). We're also [hiring](https://jobs.lever.co/shakacode/3bdbfdb3-4495-4611-a279-01dddb351abe)!
Here's a testimonial of how ShakaCode can help, from [Florian GΓΆΓler](https://github.com/FGoessler) of [Blinkist](https://www.blinkist.com/), January 2, 2023:
> Hey Justin π
>
> I just wanted to let you know that we today shipped the webpacker to shakapacker upgrades and it all seems to be running smoothly! Thanks again for all your support and your teams work! π
>
> On top of your work, it was now also very easy for me to upgrade Tailwind and include our external node_module based web component library which we were using for our other (more modern) apps already. That work is going to be shipped later this week though as we are polishing the last bits of it. π
>
> Have a great 2023 and maybe we get to work together again later in the year! π
Read the [full review here](https://clutch.co/profile/shakacode#reviews?sort_by=date_DESC#review-2118154). Here's [another review of a Shakapacker migration that led to more work](https://clutch.co/profile/shakacode#reviews?sort_by=date_DESC#review-2096078).
## Resources
* [Click to join **React + Rails Slack**](https://reactrails.slack.com/join/shared_invite/enQtNjY3NTczMjczNzYxLTlmYjdiZmY3MTVlMzU2YWE0OWM0MzNiZDI0MzdkZGFiZTFkYTFkOGVjODBmOWEyYWQ3MzA2NGE1YWJjNmVlMGE). Then join the channel `#react-rails`.
* If you are upgrading, you might consider migrating to the [react_on_rails](https://github.com/shakacode/react_on_rails) gem.
* Source code example utilizing React-Rails: https://github.com/BookOfGreg/react-rails-example-app
## Contents
- [Get started with Shakapacker](#get-started-with-shakapacker)
- [Component name](#component-name)
- [File naming](#file-naming)
- [Typescript support](#typescript-support)
- [Test component](#test-component)
- [Use with Asset Pipeline](#use-with-asset-pipeline)
- [Custom JSX Transformer](#custom-jsx-transformer)
- [Transform Plugin Options](#transform-plugin-options)
- [React.js versions](#reactjs-versions)
- [View Helper](#view-helper)
- [Custom View Helper](#custom-view-helper)
- [UJS](#ujs)
- [Mounting & Unmounting](#mounting--unmounting)
- [Event Handling](#event-handling)
- [`getConstructor`](#getconstructor)
- [Server-Side Rendering](#server-side-rendering)
- [Configuration](#configuration)
- [JavaScript State](#javascript-state)
- [Custom Server Renderer](#custom-server-renderer)
- [Controller Actions](#controller-actions)
- [Component Generator](#component-generator)
- [Use with JBuilder](#use-with-jbuilder)
- [Camelize Props](#camelize-props)
- [Changing Component Templates](#changing-component-templates)
- [Upgrading](#upgrading)
- [2.7 to 3.0](#27-to-30)
- [2.3 to 2.4](#23-to-24)
- [Other features](#other-features)
- [Replace `null` with `undefined` in props](#replace-null-with-undefined-in-props)
- [Common Errors](#common-errors)
- [Getting warning for `Can't resolve 'react-dom/client'` in React < 18](#getting-warning-for-cant-resolve-react-domclient-in-react--18)
- [Undefined Set](#undefined-set)
- [Using TheRubyRacer](#using-therubyracer)
- [HMR](#hmr)
- [Related Projects](#related-projects)
- [Contributing](#contributing)
- [Supporters](#supporters)
After reading this README file, additional information about React-Rails can be found in the Wiki page:
https://github.com/reactjs/React-Rails/wiki
The Wiki page features a significant amount of additional information about React-Rails which includes instructional articles and answers to the most frequently asked questions.
## Get started with Shakapacker
_Alternatively, get started with [Sprockets](#use-with-asset-pipeline)_
1. Create a new Rails app:
Prevent installing default javascript dependencies by using `--skip-javascript` option:
```bash
rails new my-app --skip-javascript
cd my-app
```
2. Install `shakapacker`:
```bash
bundle add shakapacker --strict
rails shakapacker:install
```
3. Install `react` and some other required npm packages:
```bash
yarn add react react-dom @babel/preset-react prop-types \
css-loader style-loader mini-css-extract-plugin css-minimizer-webpack-plugin
```
Also update the Babel configuration in the `package.json` file:
```diff
"babel": {
"presets": [
- "./node_modules/shakapacker/package/babel/preset.js"
+ "./node_modules/shakapacker/package/babel/preset.js",
+ "@babel/preset-react"
]
},
```
4. Install `react-rails`:
```bash
$ bundle add 'react-rails' --strict
$ rails generate react:install
```
This gives you:
- `app/javascript/components/` directory for your React components
- [`ReactRailsUJS`](#ujs) setup in `app/javascript/packs/application.js`
- `app/javascript/packs/server_rendering.js` for [server-side rendering](#server-side-rendering)
5. Generate your first component:
```bash
$ rails g react:component HelloWorld greeting:string
```
You can also generate your component in a subdirectory:
```bash
$ rails g react:component my_subdirectory/HelloWorld greeting:string
```
Note: Your component is added to `app/javascript/components/` by default.
Note: If your component is in a subdirectory you will append the directory path to your erb component call.
Example:
```erb
<%= react_component("my_subdirectory/HelloWorld", { greeting: "Hello from react-rails." }) %>
```
6. [Render it in a Rails view](#view-helper):
```erb
<%= react_component("HelloWorld", { greeting: "Hello from react-rails." }) %>
```
7. Lets Start the app:
```bash
$ rails s
```
Output: greeting: Hello from react-rails", inspect webpage in your browser to see the change in tag props.
8. Run dev server (optional)
In order to run dev server with HMR feature you need to parallely run:
```bash
$ ./bin/shakapacker-dev-server
```
Note: On Rails 6 you need to specify `webpack-dev-server` host. To this end, update `config/initializers/content_security_policy.rb` and uncomment relevant lines.
### Component name
The component name tells `react-rails` where to load the component. For example:
`react_component` call | component `require`
-----|-----
`react_component("Item")` | `require("Item")`
`react_component("items/index")` | `require("items/index")`
`react_component("items.Index")` | `require("items").Index`
`react_component("items.Index.Header")` | `require("items").Index.Header`
This way, you can access top-level, default, or named exports.
The `require.context` inserted into `packs/application.js` is used to load components. If you want to load components from a different directory, override it by calling `ReactRailsUJS.useContext`:
```js
var myCustomContext = require.context("custom_components", true)
var ReactRailsUJS = require("react_ujs")
// use `custom_components/` for <%= react_component(...) %> calls
ReactRailsUJS.useContext(myCustomContext)
```
If `require` fails to find your component, [`ReactRailsUJS`](#ujs) falls back to the global namespace, described in [Use with Asset Pipeline](#use-with-asset-pipeline).
In some cases, having multiple `require.context` entries may be desired. Examples of this include:
- Refactoring a typical Rails application into a Rails API with an (eventually) separate Single Page Application (SPA). For this use case, one can add a separate pack in addition to the typical `application` one. React components can be shared between the packs but the new pack can use a minimal Rails view layout, different default styling, etc.
- In a larger application, you might find it helpful to split your JavaScript by routes/controllers to avoid serving unused components and improve your site performance by keeping bundles smaller. For example, you might have separate bundles for homepage, search, and checkout routes. In that scenario, you can add an array of `require.context` component directory paths via `useContexts` to `server_rendering.js`, to allow for [Server-Side Rendering](#server-side-rendering) across your application:
```js
// server_rendering.js
var homepageRequireContext = require.context('homepage', true);
var searchRequireContext = require.context('search', true);
var checkoutRequireContext = require.context('checkout', true);
var ReactRailsUJS = require('react_ujs');
ReactRailsUJS.useContexts([
homepageRequireContext,
searchRequireContext,
checkoutRequireContext
]);
```
### File naming
React-Rails supports plenty of file extensions such as: .js, .jsx.js, .js.jsx, .es6.js, .coffee, etcetera!
Sometimes this will cause a stumble when searching for filenames.
Component File Name | `react_component` call
-----|-----
`app/javascript/components/samplecomponent.js` | `react_component("samplecomponent")`
`app/javascript/components/sample_component.js` | `react_component("sample_component")`
`app/javascript/components/SampleComponent.js` | `react_component("SampleComponent")`
`app/javascript/components/SampleComponent.js.jsx` | Has to be renamed to SampleComponent.jsx, then use `react_component("SampleComponent")`
### Typescript support
```bash
yarn add typescript @babel/preset-typescript
```
Babel wonβt perform any type-checking on TypeScript code. To optionally use type-checking run:
```bash
yarn add fork-ts-checker-webpack-plugin
```
Add `tsconfig.json` with the following content:
```json
{
"compilerOptions": {
"declaration": false,
"emitDecoratorMetadata": true,
"experimentalDecorators": true,
"lib": ["es6", "dom"],
"module": "es6",
"moduleResolution": "node",
"sourceMap": true,
"target": "es5",
"jsx": "react",
"noEmit": true
},
"exclude": ["**/*.spec.ts", "node_modules", "vendor", "public"],
"compileOnSave": false
}
```
Then modify the webpack config to use it as a plugin:
```js
// config/webpack/webpack.config.js
const { webpackConfig, merge } = require("shakapacker");
const ForkTSCheckerWebpackPlugin = require("fork-ts-checker-webpack-plugin");
module.exports = merge(webpackConfig, {
plugins: [new ForkTSCheckerWebpackPlugin()],
});
```
Doing this will allow React-Rails to support the .tsx extension. Additionally, it is recommended to add `ts` and `tsx` to the `server_renderer_extensions` in your application configuration:
```ruby
config.react.server_renderer_extensions = ["jsx", "js", "tsx", "ts"]
```
### Test component
You can use `assert_react_component` to test component render:
```erb
<%= react_component("HelloWorld", { greeting: "Hello from react-rails.", info: { name: "react-rails" } }, { class: "hello-world" }) %>
```
```rb
class WelcomeControllerTest < ActionDispatch::IntegrationTest
test 'assert_react_component' do
get "/welcome"
assert_equal 200, response.status
# assert rendered react component and check the props
assert_react_component "HelloWorld" do |props|
assert_equal "Hello from react-rails.", props[:greeting]
assert_equal "react-rails", props[:info][:name]
assert_select "[class=?]", "hello-world"
end
# or just assert component rendered
assert_react_component "HelloWorld"
end
end
```
## Use with Asset Pipeline
`react-rails` provides a pre-bundled React.js & a UJS driver to the Rails asset pipeline. Get started by adding the `react-rails` gem:
```ruby
gem 'react-rails'
```
And then install the react generator:
```
$ rails g react:install
```
Then restart your development server.
This will:
- add some `//= require`s to `application.js`
- add a `components/` directory for React components
- add `server_rendering.js` for [server-side rendering](#server-side-rendering)
Now, you can create React components in `.jsx` files:
```JSX
// app/assets/javascripts/components/post.jsx
window.Post = createReactClass({
render: function() {
return
{this.props.title}
}
})
// or, equivalent:
class Post extends React.Component {
render() {
return
{this.props.title}
}
}
```
Then, you can render those [components in views](#view-helper):
```erb
<%= react_component("Post", {title: "Hello World"}) %>
```
Components must be accessible from the top level, but they may be namespaced, for example:
```erb
<%= react_component("Comments.NewForm", {post_id: @post.id}) %>
```
### Custom JSX Transformer
`react-rails` uses a transformer class to transform JSX in the asset pipeline. The transformer is initialized once, at boot. You can provide a custom transformer to `config.react.jsx_transformer_class`. The transformer must implement:
- `#initialize(options)`, where options is the value passed to `config.react.jsx_transform_options`
- `#transform(code_string)` to return a string of transformed code
`react-rails` provides two transformers, `React::JSX::BabelTransformer` (which uses [ruby-babel-transpiler](https://github.com/babel/ruby-babel-transpiler)) and `React::JSX::JSXTransformer` (which uses the deprecated `JSXTransformer.js`).
#### Transform Plugin Options
To supply additional transform plugins to your JSX Transformer, assign them to `config.react.jsx_transform_options`
`react-rails` uses the Babel version of the `babel-source` gem.
For example, to use `babel-plugin-transform-class-properties` :
config.react.jsx_transform_options = {
optional: ['es7.classProperties']
}
### React.js versions
`//= require react` brings `React` into your project.
By default, React's [development version] is provided to `Rails.env.development`. You can override the React build with a config:
```ruby
# Here are the defaults:
# config/environments/development.rb
MyApp::Application.configure do
config.react.variant = :development
end
# config/environments/production.rb
MyApp::Application.configure do
config.react.variant = :production
end
```
Be sure to restart your Rails server after changing these files. See [VERSIONS.md](https://github.com/reactjs/react-rails/blob/master/VERSIONS.md) to learn which version of React.js is included with your `react-rails` version. In some edge cases you may need to bust the sprockets cache with `rake tmp:clear`
## View Helper
`react-rails` includes a view helper and an [unobtrusive JavaScript driver](#ujs) which work together to put React components on the page.
The view helper (`react_component`) puts a `div` on the page with the requested component class & props. For example:
```erb
<%= react_component('HelloMessage', name: 'John') %>
```
On page load, the [`react_ujs` driver](#ujs) will scan the page and mount components using `data-react-class`
and `data-react-props`.
The view helper's signature is:
```ruby
react_component(component_class_name, props={}, html_options={})
```
- `component_class_name` is a string which identifies a component. See [getConstructor](#getconstructor) for details.
- `props` is either:
- an object that responds to `#to_json`; or
- an already-stringified JSON object (see [JBuilder note](#use-with-jbuilder) below).
- `html_options` may include:
- `tag:` to use an element other than a `div` to embed `data-react-class` and `data-react-props`.
- `prerender: true` to render the component on the server.
- `camelize_props` to [transform a props hash](#camelize-props)
- `**other` Any other arguments (eg `class:`, `id:`) are passed through to [`content_tag`](http://api.rubyonrails.org/classes/ActionView/Helpers/TagHelper.html#method-i-content_tag).
#### Custom View Helper
`react-rails` uses a "helper implementation" class to generate the output of the `react_component` helper. The helper is initialized once per request and used for each `react_component` call during that request. You can provide a custom helper class to `config.react.view_helper_implementation`. The class must implement:
- `#react_component(name, props = {}, options = {}, &block)` to return a string to inject into the Rails view
- `#setup(controller_instance)`, called when the helper is initialized at the start of the request
- `#teardown(controller_instance)`, called at the end of the request
`react-rails` provides one implementation, `React::Rails::ComponentMount`.
## UJS
`react-rails`'s JavaScript is available as `"react_ujs"` in the asset pipeline or from NPM. It attaches itself to the window as `ReactRailsUJS`.
### Mounting & Unmounting
Usually, `react-rails` mounts & unmounts components automatically as described in [Event Handling](#event-handling) below.
You can also mount & unmount components from `<%= react_component(...) %>` tags using UJS:
```js
// Mount all components on the page:
ReactRailsUJS.mountComponents()
// Mount components within a selector:
ReactRailsUJS.mountComponents(".my-class")
// Mount components within a specific node:
ReactRailsUJS.mountComponents(specificDOMnode)
// Unmounting works the same way:
ReactRailsUJS.unmountComponents()
ReactRailsUJS.unmountComponents(".my-class")
ReactRailsUJS.unmountComponents(specificDOMnode)
```
You can use this when the DOM is modified by AJAX calls or modal windows.
### Event Handling
`ReactRailsUJS` checks for various libraries to support their page change events:
- `Turbolinks`
- `pjax`
- `jQuery`
- Native DOM events
`ReactRailsUJS` will automatically mount components on `<%= react_component(...) %>` tags and unmount them when appropriate.
If you need to re-detect events, you can call `detectEvents`:
```js
// Remove previous event handlers and add new ones:
ReactRailsUJS.detectEvents()
```
For example, if `Turbolinks` is loaded _after_ `ReactRailsUJS`, you'll need to call this again. This function removes previous handlers before adding new ones, so it's safe to call as often as needed.
If `Turbolinks` is `import`ed via Shakapacker (and thus not available globally), `ReactRailsUJS` will be unable to locate it. To fix this, you can temporarily add it to the global namespace:
```js
// Order is particular. First start Turbolinks:
Turbolinks.start();
// Add Turbolinks to the global namespace:
window.Turbolinks = Turbolinks;
// Remove previous event handlers and add new ones:
ReactRailsUJS.detectEvents();
// (Optional) Clean up global namespace:
delete window.Turbolinks;
```
### `getConstructor`
Components are loaded with `ReactRailsUJS.getConstructor(className)`. This function has two default implementations, depending on if you're using the asset pipeline or Shakapacker:
- On the asset pipeline, it looks up `className` in the global namespace (`ReactUJS.constructorFromGlobal`).
- On Shakapacker, it `require`s files and accesses named exports, as described in [Get started with Shakapacker](#get-started-with-shakapacker), falling back to the global namespace (`ReactUJS.constructorFromRequireContextWithGlobalFallback`).
You can override this function to customize the mapping of name-to-constructor. [Server-side rendering](#server-side-rendering) also uses this function.
For example, the fallback behavior of
`ReactUJS.constructorFromRequireContextWithGlobalFallback` can sometimes make
server-side rendering errors hard to debug as it will swallow the original error
(more info
[here](https://github.com/reactjs/react-rails/issues/264#issuecomment-552326663)).
`ReactUJS.constructorFromRequireContext` is provided for this reason. You can
use it like so:
```js
// Replaces calls to `ReactUJS.useContext`
ReactUJS.getConstructor = ReactUJS.constructorFromRequireContext(require.context('components', true));
```
## Server-Side Rendering
You can render React components inside your Rails server with `prerender: true`:
```erb
<%= react_component('HelloMessage', {name: 'John'}, {prerender: true}) %>
Hello, John!
```
_(It will also be mounted by the [UJS](#ujs) on page load.)_
Server rendering is powered by [`ExecJS`](https://github.com/rails/execjs) and subject to some requirements:
- `react-rails` must load your code. By convention, it uses `server_rendering.js`, which was created
by the install task. This file must include your components _and_ their dependencies (eg, Underscore.js).
- Requires separate compilations for server & client bundles (see [Webpack config](https://github.com/reactjs/react-rails/tree/master/test/dummy/config/webpack))
- Your code can't reference `document` or `window`. Prerender processes don't have access to `document` or `window`,
so jQuery and some other libs won't work in this environment :(
`ExecJS` supports many backends. CRuby users will get the best performance from [`mini_racer`](https://github.com/discourse/mini_racer#performance).
#### Configuration
Server renderers are stored in a pool and reused between requests. Threaded Rubies (eg jRuby) may see a benefit to increasing the pool size beyond the default `0`.
These are the default configurations:
```ruby
# config/application.rb
# These are the defaults if you don't specify any yourself
module MyApp
class Application < Rails::Application
# Settings for the pool of renderers:
config.react.server_renderer_pool_size ||= 1 # ExecJS doesn't allow more than one on MRI
config.react.server_renderer_timeout ||= 20 # seconds
config.react.server_renderer = React::ServerRendering::BundleRenderer
config.react.server_renderer_options = {
files: ["server_rendering.js"], # files to load for prerendering
replay_console: true, # if true, console.* will be replayed client-side
}
# Changing files matching these dirs/exts will cause the server renderer to reload:
config.react.server_renderer_extensions = ["jsx", "js"]
config.react.server_renderer_directories = ["/app/assets/javascripts", "/app/javascript/"]
end
end
```
#### JavaScript State
Some of ExecJS's backends are stateful (eg, mini_racer, therubyracer). This means that any side-effects of a prerender will affect later renders with that renderer.
To manage state, you have a couple options:
- Make a custom renderer with `#before_render` / `#after_render` hooks as [described below](#custom-server-renderer)
- Use `per_request_react_rails_prerenderer` to manage state for a whole controller action.
To check out a renderer for the duration of a controller action, call the `per_request_react_rails_prerenderer` helper in the controller class:
```ruby
class PagesController < ApplicationController
# Use the same React server renderer for the entire request:
per_request_react_rails_prerenderer
end
```
Then, you can access the ExecJS context directly with `react_rails_prerenderer.context`:
```ruby
def show
react_rails_prerenderer # => #
react_rails_prerenderer.context # => #
# Execute arbitrary JavaScript code
# `self` is the global context
react_rails_prerenderer.context.exec("self.Store.setup()")
render :show
react_rails_prerenderer.context.exec("self.Store.teardown()")
end
```
`react_rails_prerenderer` may also be accessed in before- or after-actions.
#### Custom Server Renderer
`react-rails` depends on a renderer class for rendering components on the server. You can provide a custom renderer class to `config.react.server_renderer`. The class must implement:
- `#initialize(options={})`, which accepts the hash from `config.react.server_renderer_options`
- `#render(component_name, props, prerender_options)` to return a string of HTML
`react-rails` provides two renderer classes: `React::ServerRendering::ExecJSRenderer` and `React::ServerRendering::BundleRenderer`.
`ExecJSRenderer` offers two other points for extension:
- `#before_render(component_name, props, prerender_options)` to return a string of JavaScript to execute _before_ calling `React.render`
- `#after_render(component_name, props, prerender_options)` to return a string of JavaScript to execute _after_ calling `React.render`
Any subclass of `ExecJSRenderer` may use those hooks (for example, `BundleRenderer` uses them to handle `console.*` on the server).
## Controller Actions
Components can also be server-rendered directly from a controller action with the custom `component` renderer. For example:
```ruby
class TodoController < ApplicationController
def index
@todos = Todo.all
render component: 'TodoList', props: { todos: @todos }, tag: 'span', class: 'todo'
end
end
```
You can also provide the "usual" `render` arguments: `content_type`, `layout`, `location` and `status`. By default, your current layout will be used and the component, rather than a view, will be rendered in place of `yield`. Custom data-* attributes can be passed like `data: {remote: true}`.
Prerendering is set to `true` by default, but can be turned off with `prerender: false`.
## Component Generator
You can generate a new component file with:
```sh
rails g react:component ComponentName prop1:type prop2:type ... [options]
```
For example,
```sh
rails g react:component Post title:string published:bool published_by:instanceOf{Person}
```
would generate:
```JSX
var Post = createReactClass({
propTypes: {
title: PropTypes.string,
published: PropTypes.bool,
publishedBy: PropTypes.instanceOf(Person)
},
render: function() {
return (
Title: {this.props.title}
Published: {this.props.published}
Published By: {this.props.publishedBy}
);
}
});
```
The generator also accepts options:
- `--es6`: generates a function component
- `--coffee`: use CoffeeScript
For example,
```sh
rails g react:component ButtonComponent title:string --es6
```
would generate:
```jsx
import React from "react"
import PropTypes from "prop-types"
function ButtonComponent(props) {
return (
Title: {this.props.title}
);
}
ButtonComponent.propTypes = {
title: PropTypes.string
};
export default ButtonComponent
```
**Note:** In a Shakapacker project, es6 template is the default template in the generator.
Accepted PropTypes are:
- Plain types: `any`, `array`, `bool`, `element`, `func`, `number`, `object`, `node`, `shape`, `string`
- `instanceOf` takes an optional class name in the form of `instanceOf{className}`.
- `oneOf` behaves like an enum, and takes an optional list of strings in the form of `'name:oneOf{one,two,three}'`.
- `oneOfType` takes an optional list of react and custom types in the form of `'model:oneOfType{string,number,OtherType}'`.
Note that the arguments for `oneOf` and `oneOfType` must be enclosed in single quotes
to prevent your terminal from expanding them into an argument list.
#### Use with JBuilder
If you use Jbuilder to pass a JSON string to `react_component`, make sure your JSON is a stringified hash,
not an array. This is not the Rails default -- you should add the root node yourself. For example:
```ruby
# BAD: returns a stringified array
json.array!(@messages) do |message|
json.extract! message, :id, :name
json.url message_url(message, format: :json)
end
# GOOD: returns a stringified hash
json.messages(@messages) do |message|
json.extract! message, :id, :name
json.url message_url(message, format: :json)
end
```
### Camelize Props
You can configure `camelize_props` option:
```ruby
MyApp::Application.configure do
config.react.camelize_props = true # default false
end
```
Now, Ruby hashes given to `react_component(...)` as props will have their keys transformed from _underscore_- to _camel_-case, for example:
```ruby
{ all_todos: @todos, current_status: @status }
# becomes:
{ "allTodos" => @todos, "currentStatus" => @status }
```
You can also specify this option in `react_component`:
```erb
<%= react_component('HelloMessage', {name: 'John'}, {camelize_props: true}) %>
```
### Changing Component Templates
To make simple changes to Component templates, copy the respective template file to your Rails project at `lib/templates/react/component/template_filename`.
For example, to change the [ES6 Component template](https://github.com/reactjs/react-rails/blob/master/lib/generators/templates/component.es6.jsx), copy it to `lib/templates/react/component/component.es6.jsx` and modify it.
## Upgrading
### 2.7 to 3.0
- Keep your `react_ujs` up to date: `yarn upgrade`
- **Drop support for Webpacker:** Before any ReactRails upgrade, make sure upgrading from Webpacker to Shakapacker 7. For more information check out Shakapacker
- **SSR:** ReactRails 3.x requires separate compilations for server & client bundles. See [Webpack config](https://github.com/reactjs/react-rails/tree/master/test/dummy/config/webpack) directory in the dummy app to addapt the new implementation.
### 2.3 to 2.4
Keep your `react_ujs` up to date, `yarn upgrade`
React-Rails 2.4.x uses React 16+ which no longer has React Addons. Therefore the pre-bundled version of react no longer has an addons version, if you need addons still, there is the 2.3.1+ version of the gem that still has addons.
If you need to make changes in your components for the prebundled react, see the migration docs here:
- https://reactjs.org/blog/2016/11/16/react-v15.4.0.html
- https://reactjs.org/blog/2017/04/07/react-v15.5.0.html
- https://reactjs.org/blog/2017/06/13/react-v15.6.0.html
For the vast majority of cases this will get you most of the migration:
- global find+replace `React.Prop` -> `Prop`
- add `import PropTypes from 'prop-types'` (Webpacker only)
- re-run `bundle exec rails webpacker:install:react` to update npm packages (Webpacker only)
## Other features
### Replace `null` with `undefined` in props
React-Rails converts `nil` to `null` while parsing props from Ruby to JavaScript. Optionally, you can configure React-Rails to parse `nil` values to `undefined` as per the following:
```ruby
# config/application.rb
module TheAppName
class Application < Rails::Application
# ...
# Set to true to convert null values in props into undefined
config.react.null_to_undefined_props = true
# ...
end
end
```
More information in: [discussion#1272](https://github.com/reactjs/react-rails/discussions/1272).
## Common Errors
### Getting warning for `Can't resolve 'react-dom/client'` in React < 18
You may see a warning like this when building a Webpack bundle using any version of React below 18. This warning can be safely [suppressed](https://webpack.js.org/configuration/other-options/#ignorewarnings) in your Webpack configuration. The following is an example of this suppression in `config/webpack/webpack.config.js`:
```diff
- const { webpackConfig } = require('shakapacker')
+ const { webpackConfig, merge } = require('shakapacker')
+const ignoreWarningsConfig = {
+ ignoreWarnings: [/Module not found: Error: Can't resolve 'react-dom\/client'/],
+};
- module.exports = webpackConfig
+ module.exports = merge({}, webpackConfig, ignoreWarningsConfig)
```
### Undefined Set
```
ExecJS::ProgramError (identifier 'Set' undefined):
(execjs):1
```
If you see any variation of this issue, see [Using TheRubyRacer](#using-therubyracer)
### Using TheRubyRacer
TheRubyRacer [hasn't updated LibV8](https://github.com/cowboyd/therubyracer/blob/master/therubyracer.gemspec#L20) (The library that powers Node.js) from v3 in 2 years, any new features are unlikely to work.
LibV8 itself is already [beyond version 7](https://github.com/cowboyd/libv8/releases/tag/v7.3.492.27.1) therefore many serverside issues are caused by old JS engines and fixed by using an up to date one such as [MiniRacer](https://github.com/discourse/mini_racer) or [TheRubyRhino](https://github.com/cowboyd/therubyrhino) on JRuby.
### HMR
Check out [Enabling Hot Module Replacement (HMR)](https://github.com/shakacode/shakapacker/blob/master/docs/react.md#enabling-hot-module-replacement-hmr) in Shakapacker documentation.
One caveat is that currently you [cannot Server-Side Render along with HMR](https://github.com/reactjs/react-rails/issues/925#issuecomment-415469572).
## Related Projects
- [webpacker-react](https://github.com/renchap/webpacker-react): Integration of React with Rails utilizing Webpack with Hot Module Replacement (HMR).
- [The React on Rails Course](https://learnetto.com/users/hrishio/courses/the-free-react-on-rails-5-course) A video course which teaches the basics of React and how to get started using it in Rails with `react-rails`.
- [react\_on\_rails](https://github.com/shakacode/react_on_rails): Integration of React with Rails utilizing Webpack, Redux, React-Router.
- [react-rails-hot-loader](https://github.com/rmosolgo/react-rails-hot-loader) Simple live-reloader for `react-rails`.
- [react-rails-benchmark_renderer](https://github.com/pboling/react-rails-benchmark_renderer) adds performance instrumentation to server rendering.
- [Ruby Hyperstack](https://hyperstack.org/): Use Ruby to build reactive user interfaces with React.
## Contributing
π Thanks for taking the time to contribute! π
With 5 Million+ downloads of the react-rails Gem and another 2 Million+ downloads of react_ujs on NPM, you're helping the biggest React + Rails community!
By contributing to React-Rails, you agree to abide by the [code of conduct](https://github.com/reactjs/react-rails/blob/master/CODE_OF_CONDUCT.md).
You can always help by submitting patches or triaging issues. Even offering reproduction steps to issues is incredibly helpful!
## Supporters
The following companies support the development of this and other open-source projects maintained by ShakaCode by providing licenses to the ShakaCode team. ShakaCode stands by the usefulness of these products!
Please see our [Contribution guide](https://github.com/reactjs/react-rails/blob/master/CONTRIBUTING.md) for more info.
