Setting Up Action Cable

Action Cable comes built into Rails. Let's configure it for development and production.

Configuration Files

Action Cable configuration lives in:

yaml
# config/cable.yml
development:
  adapter: async

test:
  adapter: test

production:
  adapter: redis
  url: <%= ENV.fetch("REDIS_URL") { "redis://localhost:6379/1" } %>
  channel_prefix: myapp_production

Adapters

• async: In-process, good for development (single server)
• redis: Production-ready, supports multiple servers
• postgresql: Uses Postgres NOTIFY/LISTEN

Mount the Server

ruby
# config/routes.rb
Rails.application.routes.draw do
  mount ActionCable.server => '/cable'

  # Your other routes...
end

The Connection Class

Handles WebSocket authentication:

ruby
# app/channels/application_cable/connection.rb
module ApplicationCable
  class Connection < ActionCable::Connection::Base
    identified_by :current_user

    def connect
      self.current_user = find_verified_user
    end

    private

    def find_verified_user
      # Session-based auth
      if verified_user = User.find_by(id: cookies.encrypted[:user_id])
        verified_user
      else
        reject_unauthorized_connection
      end
    end
  end
end

Alternative: Token Authentication

ruby
# app/channels/application_cable/connection.rb
module ApplicationCable
  class Connection < ActionCable::Connection::Base
    identified_by :current_user

    def connect
      self.current_user = find_verified_user
    end

    private

    def find_verified_user
      token = request.params[:token]
      if verified_user = User.find_by(auth_token: token)
        verified_user
      else
        reject_unauthorized_connection
      end
    end
  end
end

Client connects with:

javascript
createConsumer(`/cable?token=${userToken}`)

The Channel Base Class

ruby
# app/channels/application_cable/channel.rb
module ApplicationCable
  class Channel < ActionCable::Channel::Base
    # Shared channel logic
  end
end

Client-Side Setup

Rails generates JavaScript for Action Cable:

javascript
// app/javascript/channels/consumer.js
import { createConsumer } from "@rails/actioncable"

export default createConsumer()

Import Maps Configuration

ruby
# config/importmap.rb
pin "@rails/actioncable", to: "actioncable.esm.js"
pin_all_from "app/javascript/channels", under: "channels"

Testing Connection

Start Rails and check the console:

Started GET "/cable" [WebSocket]
Successfully upgraded to WebSocket

In browser console:

javascript
App.cable.connection.isOpen()  // true