This skill should be used when writing Ruby and Rails code in DHH's distinctive 37signals style. It applies when writing Ruby code, Rails applications, creating models, controllers, or any Ruby file. Triggers on Ruby/Rails code generation, refactoring requests, code review, or when the user mentions DHH, 37signals, Basecamp, HEY, or Campfire style. Embodies REST purity, fat models, thin controllers, Current attributes, Hotwire patterns, and the "clarity over cleverness" philosophy.
<essential_principles>
"The best code is the code you don't write. The second best is the code that's obviously correct."
Vanilla Rails is plenty:
What they deliberately avoid:
Development Philosophy:
Specify a number or describe your task. </intake>
After reading relevant references, apply patterns to the user's code. </routing>
<quick_reference>
Verbs: card.close, card.gild, board.publish (not set_style methods)
Predicates: card.closed?, card.golden? (derived from presence of related record)
Concerns: Adjectives describing capability (Closeable, Publishable, Watchable)
Controllers: Nouns matching resources (Cards::ClosuresController)
Scopes:
chronologically, reverse_chronologically, alphabetically, latestpreloaded (standard eager loading name)indexed_by, sorted_by (parameterized)active, unassigned (business terms, not SQL-ish)Instead of custom actions, create new resources:
POST /cards/:id/close → POST /cards/:id/closure
DELETE /cards/:id/close → DELETE /cards/:id/closure
POST /cards/:id/archive → POST /cards/:id/archival
# Symbol arrays with spaces inside brackets
before_action :set_message, only: %i[ show edit update destroy ]
# Private method indentation
private
def set_message
@message = Message.find(params[:id])
end
# Expression-less case for conditionals
case
when params[:before].present?
messages.page_before(params[:before])
else
messages.last_page
end
# Bang methods for fail-fast
@message = Message.create!(params)
# Ternaries for simple conditionals
@room.direct? ? @room.users : @message.mentionees
State as Records:
Card.joins(:closure) # closed cards
Card.where.missing(:closure) # open cards
Current Attributes:
belongs_to :creator, default: -> { Current.user }
Authorization on Models:
class User < ApplicationRecord
def can_administer?(message)
message.creator == self || admin?
end
end
</quick_reference>
<reference_index>
All detailed patterns in references/:
| File | Topics |
|---|---|
| controllers.md | REST mapping, concerns, Turbo responses, API patterns, HTTP caching |
| models.md | Concerns, state records, callbacks, scopes, POROs, authorization, broadcasting |
| frontend.md | Turbo Streams, Stimulus controllers, CSS layers, OKLCH colors, partials |
| architecture.md | Routing, authentication, jobs, Current attributes, caching, database patterns |
| testing.md | Minitest, fixtures, unit/integration/system tests, testing patterns |
| gems.md | What they use vs avoid, decision framework, Gemfile examples |
| </reference_index> |
<success_criteria> Code follows DHH style when:
Important Disclaimers: