# app/channels/chat_channel.rb
class ChatChannel < ApplicationCable::Channel
  def subscribed
    # Subscribe to a specific room
    room = Room.find(params[:room_id])

# Controller responding with Turbo Stream
class PostsController < ApplicationController
  def create
    @post = Post.new(post_params)

    if @post.save

class UserSearchQuery
  def initialize(relation = User.all)
    @relation = relation
  end

  def call(params)

class UserRegistrationForm
  include ActiveModel::Model
  include ActiveModel::Attributes

  attribute :email, :string
  attribute :name, :string

# Create table migration
class CreateUsers < ActiveRecord::Migration[7.0]
  def change
    create_table :users do |t|
      t.string :email, null: false, index: { unique: true }
      t.string :name, null: false

# spec/factories/users.rb
FactoryBot.define do
  factory :user do
    sequence(:email) { |n| "user#{n}@example.com" }
    name { Faker::Name.name }
    password { 'password123' }

# Basic exception handling
begin
  result = 10 / 0
rescue ZeroDivisionError => e
  puts "Error: #{e.message}"
  result = nil

# Basic matching
email = "user@example.com"
email =~ /@/  # => 4 (position of match)
email.match?(/@/)  # => true

# Capture groups

module Api
  module V1
    class UsersController < ApplicationController
      before_action :authenticate_user!, except: [:index, :show]
      before_action :set_user, only: [:show, :update, :destroy]

<%# Fragment caching - caches rendered HTML %>
<% cache @product do %>
  <h1><%= @product.name %></h1>
  <p><%= @product.description %></p>
  <p>Price: $<%= @product.price %></p>
<% end %>

# Map - transform elements
[1, 2, 3, 4].map { |n| n * 2 }          # => [2, 4, 6, 8]
['alice', 'bob'].map(&:upcase)          # => ['ALICE', 'BOB']
users.map(&:email)                       # => ['alice@example.com', ...]

# Select/Reject - filter elements

# app/validators/order_validator.rb
class OrderValidator < ActiveModel::Validator
  def validate(record)
    validate_order_total(record)
    validate_items_availability(record)
    validate_shipping_address(record)