---
name: ruby-language-idioms
description: Ruby 4+ language idioms, Enumerable patterns, blocks, classes, modules, and RuboCop-friendly style. Use when writing or refactoring Ruby outside Rails-specific APIs.
---

# Ruby Language Idioms

Write expressive, modern Ruby 4 code aligned with community style and this marketplace's tooling defaults.

## When to Use This Skill

- Refactoring Ruby for clarity
- Choosing between class methods, modules, and composition
- Explaining Ruby semantics (blocks, keywords, pattern matching)

## Defaults (This Plugin)

- **Toolchain**: mise — not rbenv, rvm, or asdf directly
- **Ruby**: 4.0.0+ unless the project pins otherwise
- **Rails**: 8+ conventions and generators when applicable
- **Execution**: Prefer `mise exec --`, `bin/rails`, `bin/rspec`, and `bundle exec`

## Core Guidance

1. **Favor readability**: Small methods, meaningful names, avoid clever one-liners.

2. **Blocks and enumerables**: Prefer `filter_map`, `index_by`, `each_with_object` over manual loops.

3. **Keyword arguments**: Use required keywords for public APIs; avoid option hashes unless interfacing with legacy APIs.

4. **Pattern matching** (Ruby 3+): Use `case/in` for structured data when it reduces nesting.

5. **Frozen string literals**: Match project pragma (`# frozen_string_literal: true`) consistently.

6. **Deprecations**: Ruby 4 continues tightening semantics — run the test suite after language upgrades.

7. **RuboCop**: Run `bundle exec rubocop` (or `mise run lint`) before large refactors.

## Quick Commands

```bash
mise exec -- ruby -e 'puts RUBY_VERSION'
mise exec -- bundle exec rubocop
mise exec -- bundle exec ruby -wc lib/
```

## Anti-Patterns

- Mutating strings when frozen literals are enabled
- `rescue Exception` or bare `rescue` without re-raise
- Metaprogramming when plain objects suffice

## See Also

- **ruby-rspec-testing** / **ruby-minitest-testing**
- **ruby-gem-development**