ruby-rails

What I do

• Enforce Rails MVC conventions with proper layer responsibilities
• Apply ActiveRecord patterns for models, validations, and associations
• Guide testing, authentication, authorization, and background job patterns

When to use me

Use this when building or maintaining Ruby on Rails applications.

Key Rules

• Use RESTful routing for all resources — follow Rails conventions
• Keep controllers thin — only HTTP concerns; move business logic to models or service objects
• Use before_action for shared setup; always use strong parameters for mass assignment
• ActiveRecord models own validations, associations, scopes, and callbacks
• Extract complex multi-step logic into Service Objects with ActiveRecord::Base.transaction
• Use scopes for reusable query logic — prefer scopes over class methods for chainability
• Use the project's test runner and fixture strategy consistently (for example RSpec + FactoryBot or Rails test + fixtures)
• Use established authN/authZ libraries (for example Devise/Sorcery/Auth0 SDK and Pundit/CanCanCan) based on project needs
• Use ActiveJob with an appropriate backend (for example Sidekiq, Solid Queue); handle missing records explicitly
• In API-only token-auth setups, CSRF is often unnecessary; do not disable CSRF globally for cookie/session flows
• Use eager loading (includes, preload) to prevent N+1 queries
• Callbacks should be simple — use deliver_later for mailers, never deliver_now in callbacks
• Migrations must have both up and down (or reversible change); add indexes on foreign keys
• Use a verify-fix-verify loop: run the validation commands below, fix any failures, and rerun until all checks pass

Naming Conventions

• snake_case for files/methods/variables
• CamelCase for classes/modules
• Service objects should use verb-oriented names (CreateInvoice, RegisterUser)
• Scope names should be intention-revealing and chain-safe

Common Pitfalls

• Fat controllers with hidden business logic
• N+1 queries due to missing eager loading
• Authorization checks scattered across controllers/views
• Long-running work executed inline instead of background jobs

Example Patterns

class RegisterUser
  def initialize(params)
    @params = params
  end

  def call
    User.transaction do
      user = User.create!(@params)
      UserProfile.create!(user:, onboarding_state: "pending")
      user
    end
  end
end

Validation Commands

Prefer project scripts when present; use defaults below otherwise.

rails test  # or project-configured test runner (e.g., rspec)
rubocop
brakeman
bundle audit