Agent skill
developing-ruby
Use when working with .rb files, Ruby gems, or implementing Ruby features. Covers Ruby idioms, naming conventions, enumerable patterns, service objects, error handling, and RSpec testing.
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/other/developing-ruby
SKILL.md
Ruby Development
Apply these patterns when working with Ruby code.
Naming Conventions
| Element | Convention | Example |
|---|---|---|
| Classes, Modules | PascalCase | UserService |
| Methods, variables | snake_case | find_user_by_id |
| Constants | SCREAMING_SNAKE | MAX_RETRIES |
| Predicates | snake_case? | active? |
| Dangerous methods | snake_case! | save! |
| Files | snake_case | user_service.rb |
Project Structure
lib/
├── my_app.rb
└── my_app/
├── version.rb
└── services/
spec/
├── spec_helper.rb
└── services/
Gemfile
Idioms
Blocks and Lambdas
users.map { |u| u.name }
users.map(&:name) # Symbol to proc
double = ->(n) { n * 2 }
double.call(5)
Enumerable
users.select(&:active?)
users.reject(&:banned?)
users.find { |u| u.id == 5 }
users.group_by(&:country)
orders.sum(&:total)
users.select(&:active?).sort_by(&:created_at).first(10).map(&:email)
Safe Navigation
user&.profile&.avatar_url
name = user.name || "Anonymous"
def expensive_calculation
@expensive_calculation ||= perform_calculation
end
Pattern Matching (Ruby 3+)
case response
in { status: 200, body: }
process(body)
in { status: 404 }
handle_not_found
end
Classes
class User
attr_reader :id, :email
attr_accessor :name
def initialize(id:, email:, name: nil)
@id = id
@email = email
@name = name
end
def active?
@status == :active
end
private
def save!
# Persist changes
end
end
Modules for Composition
module Timestampable
def touch
@updated_at = Time.current
end
end
class User
include Timestampable
end
Service Objects
class CreateUser
def initialize(user_repository:, email_service:)
@user_repository = user_repository
@email_service = email_service
end
def call(email:, name:)
user = @user_repository.create(email: email, name: name)
@email_service.send_welcome(user)
user
end
end
Error Handling
module MyApp
class Error < StandardError; end
class NotFoundError < Error; end
class ValidationError < Error
attr_reader :errors
def initialize(errors)
@errors = errors
super("Validation failed: #{errors.join(', ')}")
end
end
end
raise MyApp::NotFoundError, "User not found"
Result Objects
class Result
attr_reader :value, :error
def self.success(value) = new(value: value)
def self.failure(error) = new(error: error)
def success? = @error.nil?
def failure? = !success?
def then
return self if failure?
yield(value)
end
end
Testing with RSpec
RSpec.describe UserService do
subject(:service) { described_class.new(repository: repository) }
let(:repository) { instance_double(UserRepository) }
let(:user) { build(:user, id: 1, name: "John") }
describe "#find_by_id" do
context "when user exists" do
before { allow(repository).to receive(:find).with(1).and_return(user) }
it "returns the user" do
expect(service.find_by_id(1)).to eq(user)
end
end
end
end
Matchers
expect(result).to eq(expected)
expect(user).to be_nil
expect(list).to include(item)
expect { user.activate! }.to change(user, :status).to(:active)
expect { risky_op }.to raise_error(MyError)
Doubles
repository = instance_double(UserRepository)
allow(repository).to receive(:find).with(1).and_return(user)
mailer = instance_spy(UserMailer)
service.call
expect(mailer).to have_received(:send_welcome).with(user)
Requirements
- Use composition over inheritance
- Use keyword arguments for methods with 2+ parameters
- Return early with guard clauses
- Add
# frozen_string_literal: trueto every file - Use symbols for hash keys
- Use Enumerable methods over manual iteration
- Name predicate methods with
? - Raise exceptions only for exceptional cases; use Result objects for expected failures
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