Ruby on Rails

TL;DR

One-liner: Rails is Ruby’s opinionated full-stack framework - convention over configuration means rapid development with sensible defaults.

Core Strengths:

• Convention over configuration - less decisions, more coding
• Generators - scaffold entire features in seconds
• Active Record - elegant ORM with migrations
• Batteries included - auth, mailers, jobs, all built-in

Core Concepts

Concept 1: MVC Architecture

Models, Views, Controllers with clear separation:

# app/models/post.rb
class Post < ApplicationRecord
  validates :title, presence: true
  has_many :comments
end

# app/controllers/posts_controller.rb
class PostsController < ApplicationController
  def index
    @posts = Post.all
  end
end

# app/views/posts/index.html.erb
<% @posts.each do |post| %>
  <h2><%= post.title %></h2>
<% end %>

Concept 2: RESTful Routing

Resource-oriented routes:

# config/routes.rb
Rails.application.routes.draw do
  root "posts#index"

  resources :posts do
    resources :comments, only: [:create, :destroy]
  end

  # Generates: GET /posts, POST /posts, GET /posts/:id, etc.
end

Concept 3: Active Record

Query interface and validations:

# Queries
Post.all
Post.find(1)
Post.where(published: true).order(created_at: :desc)
Post.first(5)

# Create
Post.create(title: "Hello", body: "World")

# Update
post.update(title: "New Title")

# Associations
user.posts.create(title: "My Post")
post.comments

Quick Start

Install Rails

gem install rails

Create Project

rails new myapp
cd myapp

Generate a Resource

rails generate scaffold Post title:string body:text published:boolean
rails db:migrate

Run

rails server
# Open http://localhost:3000/posts

Gotchas

Strong parameters

class PostsController < ApplicationController
  def create
    @post = Post.new(post_params)
    if @post.save
      redirect_to @post
    else
      render :new
    end
  end

  private

  # Whitelist allowed params
  def post_params
    params.require(:post).permit(:title, :body, :published)
  end
end

Validations

class User < ApplicationRecord
  validates :email, presence: true, uniqueness: true
  validates :password, length: { minimum: 8 }
  validates :age, numericality: { greater_than: 0 }, allow_nil: true

  validate :custom_validation

  private

  def custom_validation
    errors.add(:base, "Custom error") if some_condition
  end
end

Callbacks

class Post < ApplicationRecord
  before_save :normalize_title
  after_create :send_notification

  private

  def normalize_title
    self.title = title.titleize
  end

  def send_notification
    PostMailer.new_post(self).deliver_later
  end
end

Migrations

rails generate migration AddCategoryToPosts category:string
rails db:migrate
rails db:rollback  # Undo last migration

class AddCategoryToPosts < ActiveRecord::Migration[7.0]
  def change
    add_column :posts, :category, :string
    add_index :posts, :category
  end
end

When to Use

Best for:

• Full-stack web applications
• Rapid prototyping and MVPs
• CRUD-heavy applications
• Teams wanting productivity

Not ideal for:

• Microservices (too heavy)
• Real-time apps (use Phoenix/Elixir)
• Teams unfamiliar with Ruby

Comparison:

Feature	Rails	Django	Laravel
Language	Ruby	Python	PHP
Philosophy	Convention	Explicit	Elegant
ORM	Active Record	Django ORM	Eloquent
Learning	Medium	Medium	Easy

Next Steps

• Rails Guides
• Rails Tutorial
• Rails API
• GoRails

Cheatsheet

Command	Purpose
rails new app	Create project
rails server	Start server
rails console	Interactive shell
rails generate scaffold Model	Full CRUD
rails generate model Model	Model + migration
rails generate controller Name	Controller
rails db:migrate	Run migrations
rails db:rollback	Undo migration
rails routes	Show routes
rails test	Run tests