Action Cable for real-time updates in Ruby on Rails

Introduction

Action Cable lets your Rails app send and receive live updates instantly without refreshing the page.

You want chat messages to appear instantly for all users.

You need live notifications when new data arrives.

You want to update a dashboard in real-time as data changes.

You want multiplayer game moves to show immediately to all players.

You want to show live comments or likes without page reload.

Syntax

Ruby on Rails

class ChatChannel < ApplicationCable::Channel
  def subscribed
    stream_from "chat_channel"
  end

  def unsubscribed
    # Any cleanup needed when channel is unsubscribed
  end

  def speak(data)
    ActionCable.server.broadcast "chat_channel", message: data['message']
  end
end

stream_from sets the channel to listen for broadcasts.

Methods like speak handle data sent from clients.

Examples

This streams notifications only for the current user by using their ID.

Ruby on Rails

class NotificationsChannel < ApplicationCable::Channel
  def subscribed
    stream_from "notifications_#{current_user.id}"
  end
end

This method broadcasts the received message to all subscribed clients.

Ruby on Rails

def speak(data)
  ActionCable.server.broadcast "chat_channel", message: data['message']
end

Sample Program

This example shows a simple chat channel in Rails and how the client connects and sends messages. When a message is sent, all connected clients receive it instantly.

Ruby on Rails

class ChatChannel < ApplicationCable::Channel
  def subscribed
    stream_from "chat_channel"
  end

  def speak(data)
    ActionCable.server.broadcast "chat_channel", message: data['message']
  end
end

// Client-side JavaScript example (using Rails default setup):
// app/javascript/channels/chat_channel.js
import consumer from "./consumer"

consumer.subscriptions.create("ChatChannel", {
  connected() {
    console.log("Connected to ChatChannel")
  },

  received(data) {
    console.log("New message:", data.message)
  },

  speak(message) {
    this.perform('speak', { message: message })
  }
})

// Usage in browser console:
// consumer.subscriptions.subscriptions[0].speak('Hello everyone!')

Important Notes

Remember to run bin/rails server and have Redis running for Action Cable to work smoothly.

Use stream_from carefully to avoid sending too much data to clients.

Test real-time features in multiple browser tabs to see live updates.

Summary

Action Cable adds live, real-time features to Rails apps easily.

It uses channels to send and receive messages instantly.

Clients subscribe to channels and get updates without page reloads.