What is Ruby on Rails and its core principles?

Question

Accepted Answer

**Ruby on Rails** is the dominant Ruby web framework — a full-stack, "batteries-included" framework that popularized rapid web development. It's guided by two famous principles: **Convention over Configuration** and **Don't Repeat Yourself (DRY)**, which make development fast and code consistent.

## Convention over Configuration (CoC)

```ruby
# Rails uses CONVENTIONS so you write little configuration:
class User < ApplicationRecord    # maps to the "users" table AUTOMATICALLY (convention)
end
user.posts                         # a `has_many :posts` follows naming conventions

# follow the conventions → Rails "just works" with minimal setup
# (table names, file locations, routing, etc. follow predictable patterns)
```

**Convention over Configuration**: Rails assumes sensible defaults based on naming/structure conventions (a `User` model maps to the `users` table, etc.), so you write minimal configuration. Follow the conventions and things work automatically — a huge productivity boost.

## DRY (Don't Repeat Yourself)

```text
Rails is built to avoid repetition: define things ONCE.
  ✓ A model defines the data structure used across the app
  ✓ Shared layouts/partials (don't repeat HTML)
  ✓ Validations, associations declared once on the model
  ✓ Helpers and concerns for reusable logic
```

## The MVC architecture and full stack

```text
Rails is MVC + full-stack "batteries included":
  Model (ActiveRecord ORM) — data + business logic
  View (ERB/templates) — presentation
  Controller — handles requests, coordinates
+ Routing, migrations, ActiveRecord (ORM), Action Mailer, Active Job (background jobs),
  asset pipeline, testing, security defaults — all included.
```

## ActiveRecord (the ORM) and conventions in action

```ruby
class Post < ApplicationRecord
  belongs_to :user                 # associations (convention-based)
  validates :title, presence: true # validations declared once
end

Post.where(published: true).order(:created_at)   # elegant querying
# migrations, the admin-like console, generators (scaffolding) all boost productivity
```

## Why it matters

Understanding Ruby on Rails and its core principles is important because Rails is the **dominant Ruby web framework** and the primary reason Ruby became popular for web development — it's what most professional Ruby web work involves, and it profoundly influenced web frameworks across many languages.

Rails' guiding principles are its defining philosophy and worth understanding deeply: **Convention over Configuration** (Rails assumes sensible defaults based on naming and structure conventions, so following them means writing minimal configuration while things "just work" — a major productivity boost that lets developers build features fast) and **DRY (Don't Repeat Yourself)** (defining things once — a model drives data structure, validations, and associations used throughout the app).

These principles, combined with Rails' **full-stack, batteries-included** nature (MVC architecture, the ActiveRecord ORM, routing, migrations, background jobs, security defaults, generators — everything needed for a web app), are why Rails enables rapid, productive development and consistent codebases.

Understanding Rails' philosophy (CoC and DRY), its MVC structure, ActiveRecord (the elegant, convention-based ORM), and the productivity its conventions and included tooling provide is important for any Ruby web development.

Since Rails is the framework that defines Ruby's web presence (powering countless startups and applications), embodies influential principles that shaped the broader web-framework world, and is where most professional Ruby development happens, understanding it and its core principles is essential, frequently-relevant knowledge for Ruby developers — it's the practical context in which Ruby is most used, and grasping its convention-driven, DRY, batteries-included philosophy is foundational for productive Rails development and a common, important topic reflecting understanding of Ruby's flagship framework.