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The Unofficial 37signals/DHH Rails Style Guide

About This Document

This style guide was generated by Claude Code through deep analysis of the Fizzy codebase - 37signals' open-source project management tool.

Why Fizzy matters: While 37signals has long advocated for "vanilla Rails" and opinionated software design, their production codebases (Basecamp, HEY, etc.) have historically been closed source. Fizzy changes that. For the first time, developers can study a real 37signals/DHH-style Rails application - not just blog posts and conference talks, but actual production code with all its patterns, trade-offs, and deliberate omissions.

How this was created: Claude Code analyzed the entire codebase - routes, controllers, models, concerns, views, JavaScript, CSS, tests, and configuration. The goal was to extract not just what patterns are used, but why - inferring philosophy from implementation choices.

Elixir Cheat Sheet

See the Official Guides.

Getting Started

Command Line

Start a REPL: iex

>>> docker exec -it CONTAINERID /bin/sh
/app # telnet
/bin/sh: telnet: not found

/app # apk update
fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/community/x86_64/APKINDEX.tar.gz
v3.7.0-243-gf26e75a186 [http://dl-cdn.alpinelinux.org/alpine/v3.7/main]
v3.7.0-229-g087f28e29d [http://dl-cdn.alpinelinux.org/alpine/v3.7/community]

Build Server

Go to Digital Ocean
Create new droplet
London
Ubuntu
No apps
Add SSH keys

Tested with Phoenix 1.3

1) Installing sass, font-awesome and bootstrap package's using Brunch

First, install the Sass, Font Awesome, bootstrap(and deps) package:

cd assets

npm install --save-dev sass-brunch
npm install --save font-awesome

Rails request path cheatsheet

Full path with query string

>>  request.url
=> "http://localhost:3000/ask-help.amp?ptn=pnh"

Virtual path without query string

>>  request.path
=&gt; "/ask-help.amp"

Notes on learning Elixir and Phoenix

Just some assorted notes I've made while digging into Phoenix, Elixir and friends. I'm coming from a strong Rails background, so many of these will refer to features from that framework.

Views / Templates

Biggest difference from Rails?

Unlike Rails, where rendering is almost always performed by a template file, the responsibility of rendering a response in Phoenix lies with a view module (that typically corresponds to the current controller module.) This view module will typically offer a whole bunch of render functions (matching different parameters, first and foremost the template name.) Templates (found in web/templates/) will directly compile into such functions.

	class AttachedValidator < ActiveModel::EachValidator
	def validate_each(record, attribute, value)
	record.errors.add(attribute, :attached, options) unless value.attached?
	end
	end

	require 'hexapdf'

	doc = HexaPDF::Document.open("/home/xxxx/Downloads/OoPdfFormExample.pdf")
	page = doc.pages[0]
	canvas = page.canvas(type: :overlay)


	canvas.translate(0, 20) do
	canvas.fill_color(0.3, 0.7, 0.7)
	canvas.rectangle(50, 0, 80, 80, radius: 80)

	FROM ruby:2.3.1

	# Install dependencies
	RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs

	# Set an environment variable where the Rails app is installed to inside of Docker image:
	ENV RAILS_ROOT /var/www/app_name
	RUN mkdir -p $RAILS_ROOT

	# Set working directory, where the commands will be ran: