Inertia Rails

What is Inertia Rails

Inertia Rails is a hybrid approach that combines Rails server-side routing with React client-side views. It's not a traditional SPA (no client-side routing) and not traditional SSR (no server-side rendering).

How it works:

• Rails handles routing, controllers, authentication, data fetching
• React components replace ERB templates as the view layer
• Inertia intercepts link clicks and makes XHR requests
• Server returns JSON with component name and props instead of HTML
• Client dynamically swaps components without full page reload

Component location: app/frontend/pages/ControllerName/ActionName.jsx

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Responses & Props

Basic Inertia Response

# Automatic component resolution: users/show.jsx
def show
  user = User.find(params[:id])
  render inertia: { user: }
end

Explicit Component Names

def my_event
  event = Event.find(params[:id])
  render inertia: 'events/show', props: { event: }
end

View Data for ERB Templates

def show
  event = Event.find(params[:id])
  render inertia: { event: }, view_data: { meta: event.meta }
end

⚠️ Security Warning: All props are visible client-side. Never include sensitive data in props.

---

Redirects

Always redirect after form submissions. Inertia automatically handles 303 responses.

def create
  user = User.new(user_params)
  
  if user.save
    redirect_to users_url
  else
    redirect_to new_user_url, inertia: { errors: user.errors }
  end
end

External Redirects

Use inertia_location for external URLs or non-Inertia endpoints:

inertia_location external_service_url

---

Forms

Form Component

Use <Form> for simple forms that behave like HTML forms:

import { Form } from '@inertiajs/react'

<Form action="/users" method="post">
  <input type="text" name="name" />
  <input type="email" name="email" />
  <button type="submit">Create User</button>
</Form>

Key props:

• action, method: Form endpoint
• resetOnSuccess: Reset form after successful submission
• transform: Modify data before submission
• onSuccess, onError: Event callbacks

Slot props for state:

<Form action="/users" method="post">
  {({ errors, processing, wasSuccessful }) => (
    <>
      <input type="text" name="name" />
      {errors.name && <div>{errors.name}</div>}
      <button type="submit" disabled={processing}>
        {processing ? 'Creating...' : 'Create User'}
      </button>
      {wasSuccessful && <div>User created!</div>}
    </>
  )}
</Form>

useForm Helper

Use useForm for programmatic control and complex forms:

import { useForm } from '@inertiajs/react'

const { data, setData, post, processing, errors, reset } = useForm({
  name: '',
  email: '',
})

function submit(e) {
  e.preventDefault()
  post('/users', {
    onSuccess: () => reset('password'),
  })
}

return (
  <form onSubmit={submit}>
    <input
      value={data.name}
      onChange={(e) => setData('name', e.target.value)}
    />
    {errors.name && <div>{errors.name}</div>}
    <button type="submit" disabled={processing}>Submit</button>
  </form>
)

Key methods:

• get, post, put, patch, delete: Submit form
• setData: Update form data
• reset: Reset to default values
• clearErrors: Clear validation errors
• setError: Manually set errors

Validation Errors

Rails automatically populates errors when validation fails:

# Controller - errors automatically available in frontend
def create
  user = User.new(user_params)
  if user.save
    redirect_to users_url
  else
    redirect_to new_user_url, inertia: { errors: user.errors }
  end
end

---

Deferred & Lazy Props

Server-side Deferred Props

Use InertiaRails.defer for data that loads after initial render:

def index
  render inertia: {
    users: -> { User.all },
    permissions: InertiaRails.defer { Permission.all },
  }
end

Client-side Deferred Component

import { Deferred } from '@inertiajs/react'

<Deferred data="permissions" fallback={<div>Loading...</div>}>
  <PermissionsComponent />
</Deferred>

WhenVisible for Lazy Loading

import { WhenVisible } from '@inertiajs/react'

<WhenVisible data="permissions" fallback={<div>Loading...</div>}>
  <PermissionsComponent />
</WhenVisible>

---

Navigation

Link Component

Replace <a> with <Link> for Inertia navigation:

import { Link } from '@inertiajs/react'

<Link href="/users">Users</Link>
<Link href="/users/new" method="post" as="button">New User</Link>

Programmatic Navigation

import { router } from '@inertiajs/react'

router.visit('/users')
router.post('/users', data)
router.visit('/users', { only: ['users'] }) // Partial reload

---

Flash Messages

Setting Flash Messages

def create
  user = User.new(user_params)
  if user.save
    redirect_to users_url, notice: 'User created successfully!'
  else
    redirect_to new_user_url, inertia: { 
      errors: user.errors,
      alert: 'Failed to create user'
    }
  end
end

Accessing Flash Messages

Flash messages are automatically available as props:

// In your layout or page component
export default function Layout({ children, flash }) {
  return (
    <div>
      {flash.notice && <div className="notice">{flash.notice}</div>}
      {flash.alert && <div className="alert">{flash.alert}</div>}
      {children}
    </div>
  )
}

---

Routes

Shorthand Routes

Route directly to components without controllers:

# config/routes.rb
inertia 'dashboard' => 'Dashboard'
inertia :settings  # Maps to Settings component

namespace :admin do
  inertia 'dashboard' => 'Admin/Dashboard'
end

resources :users do
  inertia :activity, on: :member
end

URL Generation

Generate URLs server-side and include as props:

def index
  render inertia: {
    users: User.all.map { |user| 
      user.as_json(only: [:id, :name]).merge(edit_url: edit_user_path(user))
    },
    create_url: new_user_path
  }
end

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