Dhh Rails Style

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name: dhh-rails-style description: 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.

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Apply 37signals/DHH Rails conventions to Ruby and Rails code. This skill provides comprehensive domain expertise extracted from analyzing production 37signals codebases (Fizzy/Campfire) and DHH's code review patterns.

Core Philosophy

"The best code is the code you don't write. The second best is the code that's obviously correct."

Vanilla Rails is plenty:

Rich domain models over service objects

CRUD controllers over custom actions

Concerns for horizontal code sharing

Records as state instead of boolean columns

Database-backed everything (no Redis)

Build solutions before reaching for gems

What they deliberately avoid:

devise (custom ~150-line auth instead)

pundit/cancancan (simple role checks in models)

sidekiq (Solid Queue uses database)

redis (database for everything)

view_component (partials work fine)

GraphQL (REST with Turbo sufficient)

factory_bot (fixtures are simpler)

rspec (Minitest ships with Rails)

Tailwind (native CSS with layers)

Development Philosophy:

Ship, Validate, Refine - prototype-quality code to production to learn

Fix root causes, not symptoms

Write-time operations over read-time computations

Database constraints over ActiveRecord validations

What are you working on?

1. Controllers - REST mapping, concerns, Turbo responses, API patterns 2. Models - Concerns, state records, callbacks, scopes, POROs 3. Views & Frontend - Turbo, Stimulus, CSS, partials 4. Architecture - Routing, multi-tenancy, authentication, jobs, caching 5. Testing - Minitest, fixtures, integration tests 6. Gems & Dependencies - What to use vs avoid 7. Code Review - Review code against DHH style 8. General Guidance - Philosophy and conventions

Specify a number or describe your task.

| Response | Reference to Read | |----------|-------------------| | 1, controller | controllers.md | | 2, model | models.md | | 3, view, frontend, turbo, stimulus, css | frontend.md | | 4, architecture, routing, auth, job, cache | architecture.md | | 5, test, testing, minitest, fixture | testing.md | | 6, gem, dependency, library | gems.md | | 7, review | Read all references, then review code | | 8, general task | Read relevant references based on context |

After reading relevant references, apply patterns to the user's code.

Naming Conventions

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, latest

preloaded (standard eager loading name)

indexed_by, sorted_by (parameterized)

active, unassigned (business terms, not SQL-ish)

REST Mapping

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

Ruby Syntax Preferences

# 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

Key Patterns

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

Domain Knowledge

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 |

Code follows DHH style when:

Controllers map to CRUD verbs on resources

Models use concerns for horizontal behavior

State is tracked via records, not booleans

No unnecessary service objects or abstractions

Database-backed solutions preferred over external services

Tests use Minitest with fixtures

Turbo/Stimulus for interactivity (no heavy JS frameworks)

Native CSS with modern features (layers, OKLCH, nesting)

Authorization logic lives on User model

Jobs are shallow wrappers calling model methods

Based on The Unofficial 37signals/DHH Rails Style Guide by Marc Köhlbrugge, generated through deep analysis of 265 pull requests from the Fizzy codebase.

Important Disclaimers:

LLM-generated guide - may contain inaccuracies

Code examples from Fizzy are licensed under the O'Saasy License

Not affiliated with or endorsed by 37signals