Convention over configuration principle in Ruby on Rails

Introduction

This principle helps you write less setup code by following common rules. Rails knows what to do if you follow its naming and structure.

When creating a new Rails app and you want to avoid writing extra setup code.

When naming files and folders in your Rails project to make things work automatically.

When you want Rails to guess your database table names from your model names.

When you want to speed up development by trusting Rails defaults.

When you want your team to follow the same simple rules to avoid confusion.

Syntax

Ruby on Rails

No special code syntax; it means following Rails naming and folder rules.

For example, a model named Article uses a database table named articles automatically.

Controllers named ArticlesController handle views in app/views/articles/ folder by default.

Examples

Rails expects the database table to be named articles automatically.

Ruby on Rails

# Model file: app/models/article.rb
class Article < ApplicationRecord
end

Rails looks for the view template in app/views/articles/index.html.erb by default.

Ruby on Rails

# Controller file: app/controllers/articles_controller.rb
class ArticlesController < ApplicationController
  def index
    @articles = Article.all
  end
end

Rails uses the table name articles matching the model Article.

Ruby on Rails

# Migration file: db/migrate/20240101000000_create_articles.rb
class CreateArticles < ActiveRecord::Migration[7.0]
  def change
    create_table :articles do |t|
      t.string :title
      t.text :content
      t.timestamps
    end
  end
end

Sample Program

This example shows a Post model, a controller PostsController, and a view in app/views/posts/index.html.erb. Rails connects them automatically because of the naming conventions.

Ruby on Rails

# app/models/post.rb
class Post < ApplicationRecord
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>
  <p><%= post.content %></p>
<% end %>

Important Notes

Following Rails conventions saves time and reduces errors.

You can override conventions, but it requires extra configuration.

Always name files, classes, and folders carefully to match Rails expectations.

Summary

Rails uses conventions to guess what you want, so you write less setup code.

Models, controllers, views, and database tables follow naming rules to connect automatically.

Following these rules helps you build apps faster and with fewer mistakes.