Andrew Kane Gem Writer Write Ruby gems following Andrew Kane's battle-tested patterns from 100+ gems with 374M+ downloads (Searchkick, PgHero, Chartkick, Strong Migrations, Lockbox, Ahoy, Blazer, Groupdate, Neighbor, Blind Index). Core Philosophy Simplicity over cleverness. Zero or minimal dependencies. Explicit code over metaprogramming. Rails integration without Rails coupling. Every pattern serves production use cases. Entry Point Structure Every gem follows this exact pattern in lib/gemname.rb :

1. Dependencies (stdlib preferred)

require "forwardable"

2. Internal modules

require_relative "gemname/model" require_relative "gemname/version"

3. Conditional Rails (CRITICAL - never require Rails directly)

require_relative "gemname/railtie" if defined ? ( Rails )

4. Module with config and errors

module GemName class Error < StandardError ; end class InvalidConfigError < Error ; end class << self attr_accessor :timeout , :logger attr_writer :client end self . timeout = 10

Defaults set immediately

end Class Macro DSL Pattern The signature Kane pattern—single method call configures everything:

Usage

class Product < ApplicationRecord searchkick word_start : [ :name ] end

Implementation

module GemName module Model def gemname ( ** options ) unknown = options . keys - KNOWN_KEYWORDS raise ArgumentError , "unknown keywords:

{

unknown . join ( ", " ) } " if unknown . any ? mod = Module . new mod . module_eval do define_method :some_method do

implementation

end unless method_defined ? ( :some_method ) end include mod class_eval do cattr_reader :gemname_options , instance_reader : false class_variable_set : @@gemname_options , options . dup end end end end Rails Integration Always use ActiveSupport.on_load —never require Rails gems directly:

WRONG

require "active_record" ActiveRecord :: Base . include ( MyGem :: Model )

CORRECT

ActiveSupport . on_load ( :active_record ) do extend GemName :: Model end

Use prepend for behavior modification

ActiveSupport . on_load ( :active_record ) do ActiveRecord :: Migration . prepend ( GemName :: Migration ) end Configuration Pattern Use class << self with attr_accessor , not Configuration objects: module GemName class << self attr_accessor :timeout , :logger attr_writer :master_key end def self . master_key @master_key ||= ENV [ "GEMNAME_MASTER_KEY" ] end self . timeout = 10 self . logger = nil end Error Handling Simple hierarchy with informative messages: module GemName class Error < StandardError ; end class ConfigError < Error ; end class ValidationError < Error ; end end

Validate early with ArgumentError

def initialize ( key : ) raise ArgumentError , "Key must be 32 bytes" unless key &. bytesize == 32 end Testing (Minitest Only)

test/test_helper.rb

require "bundler/setup" Bundler . require ( :default ) require "minitest/autorun" require "minitest/pride"

test/model_test.rb

class ModelTest < Minitest :: Test def test_basic_functionality assert_equal expected , actual end end Gemspec Pattern Zero runtime dependencies when possible: Gem :: Specification . new do | spec | spec . name = "gemname" spec . version = GemName :: VERSION spec . required_ruby_version = ">= 3.1" spec . files = Dir [ ".{md,txt}" , "{lib}//" ] spec . require_path = "lib"

NO add_dependency lines - dev deps go in Gemfile

end Anti-Patterns to Avoid method_missing (use define_method instead) Configuration objects (use class accessors) @@class_variables (use class << self ) Requiring Rails gems directly Many runtime dependencies Committing Gemfile.lock in gems RSpec (use Minitest) Heavy DSLs (prefer explicit Ruby) Reference Files For deeper patterns, see: references/module-organization.md - Directory layouts, method decomposition references/rails-integration.md - Railtie, Engine, on_load patterns references/database-adapters.md - Multi-database support patterns references/testing-patterns.md - Multi-version testing, CI setup references/resources.md - Links to Kane's repos and articles