ruby

name	ruby
description	This skill should be used when writing or reviewing Ruby code, or when the project uses "Ruby", "RSpec", "service objects", "Struct", "Data class", or Ruby class/module patterns. Provides Ruby coding conventions, patterns, and best practices. Project-specific conventions always take priority.
version	0.1.0

Ruby Conventions

Coding conventions and best practices for Ruby projects. Project-specific conventions (CLAUDE.md, style guides) always take priority over this guidance.

File Structure

• Explicit require statements at top of file

Naming

• Class names in PascalCase, method names in snake_case
• File paths matching class hierarchy (e.g., lib/my_app/user_service.rb for MyApp::UserService)
• Constants in SCREAMING_SNAKE_CASE

Architecture & Design

• Service objects: Command/service pattern for encapsulating business logic outside models
• Module structure: Namespace hierarchy; include for instance behavior, extend for class behavior
• Data structures: Struct or Data classes for value objects instead of raw hashes

Methods

• Keyword arguments for methods with multiple parameters
• def self.method_name for class methods
• Guard clauses for early returns on precondition checks
• attr_reader over direct instance variable access
• Short single-line methods when appropriate

Data Handling

• Hash#fetch and Array#fetch for required keys/indexes
• Omit hash value when identical to key: {foo:} instead of {foo: foo}
• Consistent hash syntax with symbol keys and colons

Error Handling

• Rescue specific exceptions only (e.g., Aws::S3::Errors::NoSuchKey), never rescue Exception or bare rescue
• Raise with descriptive messages
• Let exceptions propagate unless there is a meaningful reason to catch them:
  • Adding context to the error
  • Performing cleanup operations
  • Converting one exception type to another
  • Recovering from expected error conditions

Nil Handling

• Explicit nil checks vs safe navigation (&.) vs fetch with defaults
• Prefer fetch to surface unexpected missing keys early

Testing — RSpec

• Describe/context/it hierarchy; spec file placement mirroring source tree
• Factory patterns for test data; understand let (lazy) vs let! (eager) semantics
• Cover error paths and edge cases: nil inputs, empty collections, boundary values
• Spec examples for each documented error condition

AWS SDK

• Lazy initialize AWS clients as instance variables
• Pass logger to AWS clients
• Use symbolized keys for AWS responses
• In AWS Lambda contexts, initialize with dependency injection via environment: parameter

Logging

• Use structured logging with JSON when appropriate
• Log important operations (locks, state changes)

Security

• Credential hashing: bcrypt or argon2 for passwords
• Token storage: Hashed tokens in database, plaintext never persisted
• Constant-time comparison: ActiveSupport::SecurityUtils.secure_compare or equivalent for secret comparison