Rails Conventions

Comprehensive guide to Ruby on Rails conventions, the Rails Way philosophy, and best practices for organizing Rails 7+ applications.

Core Philosophy

Rails follows "Convention over Configuration" - sensible defaults reduce decision fatigue and boilerplate. Learn the conventions to write less code and collaborate effectively.

The Rails Way Principles

1. DRY (Don't Repeat Yourself) - Extract duplication into helpers, concerns, or services
2. Convention over Configuration - Follow naming patterns, get automatic wiring
3. Fat Models, Skinny Controllers - Business logic in models, controllers handle HTTP
4. RESTful Design - Resources map to standard CRUD actions

File Structure (Rails 7+)

app/
├── controllers/          # Handle HTTP requests
│   ├── concerns/         # Shared controller modules
│   └── application_controller.rb
├── models/               # Business logic and data
│   ├── concerns/         # Shared model modules
│   └── application_record.rb
├── views/                # Templates
│   ├── layouts/          # Page wrappers
│   └── shared/           # Partials used across views
├── helpers/              # View helper methods
├── mailers/              # Email logic
├── jobs/                 # Background jobs (ActiveJob)
├── channels/             # ActionCable WebSocket channels
└── javascript/           # Hotwire/Stimulus (import maps)
    └── controllers/      # Stimulus controllers

config/
├── routes.rb             # URL routing
├── database.yml          # Database configuration
├── credentials.yml.enc   # Encrypted secrets
└── initializers/         # Startup configuration

db/
├── migrate/              # Database migrations
├── schema.rb             # Current schema (auto-generated)
└── seeds.rb              # Seed data

lib/
├── tasks/                # Custom Rake tasks
└── [custom modules]      # Non-Rails-specific code

test/                     # Tests (Minitest)

Naming Conventions

Models

Convention	Example	Notes
Class name	User, BlogPost	Singular, CamelCase
File name	user.rb, blog_post.rb	Singular, snake_case
Table name	users, blog_posts	Plural, snake_case
Foreign key	user_id, blog_post_id	Singular + _id

Controllers

Convention	Example	Notes
Class name	UsersController	Plural + Controller
File name	users_controller.rb	Plural, snake_case
Actions	index, show, new, create, edit, update, destroy	RESTful

Views

Convention	Example
Directory	app/views/users/
Template	index.html.erb, show.html.erb
Partial	_user.html.erb, _form.html.erb
Layout	application.html.erb

RESTful Routes

Standard resource routes map to controller actions:

# config/routes.rb
resources :articles do
  resources :comments, only: [:create, :destroy]
end

HTTP Verb	Path	Controller#Action	Purpose
GET	/articles	articles#index	List all
GET	/articles/new	articles#new	New form
POST	/articles	articles#create	Create
GET	/articles/:id	articles#show	Show one
GET	/articles/:id/edit	articles#edit	Edit form
PATCH/PUT	/articles/:id	articles#update	Update
DELETE	/articles/:id	articles#destroy	Delete

Custom Routes

Add member and collection routes when needed:

resources :articles do
  member do
    post :publish      # POST /articles/:id/publish
  end
  collection do
    get :drafts        # GET /articles/drafts
  end
end

Controller Conventions

Standard Controller Pattern

class ArticlesController < ApplicationController
  before_action :set_article, only: [:show, :edit, :update, :destroy]

  def index
    @articles = Article.all
  end

  def show; end

  def new
    @article = Article.new
  end

  def create
    @article = Article.new(article_params)
    if @article.save
      redirect_to @article, notice: "Article created."
    else
      render :new, status: :unprocessable_entity
    end
  end

  def edit; end

  def update
    if @article.update(article_params)
      redirect_to @article, notice: "Article updated."
    else
      render :edit, status: :unprocessable_entity
    end
  end

  def destroy
    @article.destroy
    redirect_to articles_url, notice: "Article deleted."
  end

  private

  def set_article
    @article = Article.find(params[:id])
  end

  def article_params
    params.require(:article).permit(:title, :body, :published)
  end
end

Strong Parameters

Always whitelist permitted parameters:

def article_params
  params.require(:article).permit(:title, :body, :published, tag_ids: [])
end

Model Conventions

Standard Model Structure

class Article < ApplicationRecord
  # Constants first
  STATUSES = %w[draft published archived].freeze

  # Associations
  belongs_to :author, class_name: "User"
  has_many :comments, dependent: :destroy
  has_many :taggings, dependent: :destroy
  has_many :tags, through: :taggings

  # Validations
  validates :title, presence: true, length: { maximum: 255 }
  validates :body, presence: true
  validates :status, inclusion: { in: STATUSES }

  # Callbacks (use sparingly)
  before_validation :normalize_title
  after_create :notify_subscribers

  # Scopes
  scope :published, -> { where(status: "published") }
  scope :recent, -> { order(created_at: :desc) }
  scope :by_author, ->(author) { where(author: author) }

  # Class methods
  def self.search(query)
    where("title ILIKE ?", "%#{query}%")
  end

  # Instance methods
  def publish!
    update!(status: "published", published_at: Time.current)
  end

  private

  def normalize_title
    self.title = title&.strip&.titleize
  end

  def notify_subscribers
    ArticleNotificationJob.perform_later(self)
  end
end

Concerns

Extract shared behavior into concerns:

# app/models/concerns/publishable.rb
module Publishable
  extend ActiveSupport::Concern

  included do
    scope :published, -> { where.not(published_at: nil) }
    scope :draft, -> { where(published_at: nil) }
  end

  def published?
    published_at.present?
  end

  def publish!
    update!(published_at: Time.current)
  end
end

# app/models/article.rb
class Article < ApplicationRecord
  include Publishable
end

Service Objects

For complex business logic, use service objects in app/services/:

# app/services/article_publisher.rb
class ArticlePublisher
  def initialize(article, user:)
    @article = article
    @user = user
  end

  def call
    return failure("Not authorized") unless @user.can_publish?(@article)
    return failure("Already published") if @article.published?

    ActiveRecord::Base.transaction do
      @article.publish!
      notify_subscribers
      track_analytics
    end

    success(@article)
  rescue StandardError => e
    failure(e.message)
  end

  private

  def notify_subscribers
    # notification logic
  end

  def track_analytics
    # analytics logic
  end

  def success(result)
    OpenStruct.new(success?: true, result: result)
  end

  def failure(error)
    OpenStruct.new(success?: false, error: error)
  end
end

Where to Put Code

Code Type	Location	Example
Business logic	Models or Services	Validation, calculations
HTTP handling	Controllers	Params, redirects, rendering
View formatting	Helpers or View Components	Date formatting, HTML helpers
Background work	Jobs	Email sending, API calls
Database queries	Models (scopes)	Complex queries
External APIs	lib/ or Services	API wrappers
Shared behavior	Concerns	Reusable modules

Best Practices

1. Keep controllers thin - Move logic to models or services
2. Use scopes - Named queries are reusable and testable
3. Validate early - Database constraints + model validations
4. Use concerns wisely - For truly shared behavior, not just to shrink files
5. Prefer composition - Service objects over massive models
6. Follow REST - Custom actions are a smell; consider new resources

Additional Resources

Reference Files

• references/advanced-patterns.md - Service objects, query objects, form objects
• references/code-organization.md - When models get too big