Rails Models

Rails Models (ActiveRecord)

Quick Reference

| Pattern | Example | |---------|---------| | Model Generation | rails g model User name:string email:string | | Migration | rails g migration AddAgeToUsers age:integer | | Validation | validates :email, presence: true, uniqueness: true | | Association | has_many :posts, dependent: :destroy | | Callback | before_save :normalize_email | | Scope | scope :active, -> { where(active: true) } | | Query | User.where(active: true).order(created_at: :desc) |

Model Definition

class User  { where(active: true) }
  scope :recent, -> { order(created_at: :desc) }
  
  # Class methods
  def self.search(query)
    where("name ILIKE ?", "%#{query}%")
  end
  
  # Instance methods
  def full_name
    "#{first_name} #{last_name}"
  end
  
  private
  
  def normalize_email
    self.email = email.downcase.strip
  end
end

Migrations

Creating Tables

class CreateUsers  { where(published: true) }, class_name: 'Book'
end

class Book  { where(published: true) }
  scope :recent, -> { order(created_at: :desc) }
  scope :by_author, ->(author_id) { where(author_id: author_id) }
  scope :created_between, ->(start_date, end_date) {
    where(created_at: start_date..end_date)
  }
  
  # Chaining scopes
  # Post.published.recent.limit(10)
end

# Query methods
Post.where(published: true)
Post.where("views > ?", 100)
Post.where(author_id: [1, 2, 3])
Post.where.not(category: 'draft')

# Ordering
Post.order(created_at: :desc)
Post.order(views: :desc, created_at: :asc)

# Limiting
Post.limit(10)
Post.offset(20).limit(10)

# Joins
Post.joins(:author)
Post.joins(:author, :comments)
Post.left_joins(:comments)

# Includes (eager loading)
Post.includes(:author, :comments)
Post.includes(author: :profile)

# Selecting specific fields
Post.select(:id, :title, :created_at)
Post.pluck(:title)
Post.pluck(:id, :title)

# Aggregations
Post.count
Post.average(:views)
Post.maximum(:views)
Post.minimum(:views)
Post.sum(:views)

# Group
Post.group(:category).count
Post.group(:author_id).average(:views)

Enums

class Post < ApplicationRecord
  enum status: {
    draft: 0,
    published: 1,
    archived: 2
  }
  
  # Or with prefix/suffix
  enum visibility: {
    public: 0,
    private: 1
  }, _prefix: :visibility
  
  # Usage:
  # post.draft!
  # post.published?
  # Post.published
  # post.visibility_public!
end

Model Concerns

# app/models/concerns/taggable.rb
module Taggable
  extend ActiveSupport::Concern
  
  included do
    has_many :taggings, as: :taggable
    has_many :tags, through: :taggings
  end
  
  class_methods do
    def tagged_with(tag_name)
      joins(:tags).where(tags: { name: tag_name })
    end
  end
  
  def tag_list
    tags.pluck(:name).join(', ')
  end
end

# Usage in model
class Post < ApplicationRecord
  include Taggable
end

Best Practices

1. Fat models, skinny controllers - Business logic belongs in models
2. Use scopes for common queries
3. Validate at database level with constraints when possible
4. Use indexes for frequently queried columns
5. Eager load associations to avoid N+1 queries
6. Use concerns to share behavior across models
7. Keep callbacks simple - avoid complex logic
8. Use transactions for multi-step operations
9. Avoid callbacks for cross-cutting concerns - use service objects instead

Common Pitfalls

• N+1 queries: Use includes, preload, or eager_load
• Callback hell: Keep callbacks simple, use service objects for complex logic
• Mass assignment vulnerabilities: Use strong parameters in controllers
• Missing indexes: Add indexes for foreign keys and frequently queried columns
• Ignoring database constraints: Add NOT NULL, unique constraints in migrations

References

• Rails Guides - Active Record
• Rails Guides - Validations
• Rails Guides - Associations
• Rails Guides - Migrations
• Rails Guides - Queries

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: Shoebtamboli
• Source: Shoebtamboli/railsclaude_skills
• License: MIT
• Homepage: https://rubygems.org/gems/railsclaudeskills

Install and usage instructions live in the source repository linked above.