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http://www.flickr.com/photos/xt0ph3r/3591242324 modularizing rails apps kevin shekleton @kpshek

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@kpshek

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Modularizing
 Rails Apps

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Oregon

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2007 Rails 2.0

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class Plugin • The junk drawer of Rails apps • Code copied into
 your_app/vendor/plugins • Often managed via rake tasks or git submodules • Encourages local editing http://www.flickr.com/photos/listener42/3488807301

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2007 Rails 2.0 2009 Rails 2.3 Full engines

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2005 2007 Rails 2.0 2009 Rails 2.3 Engine concept introduced Full engines

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2005: Rails Engines Plugin

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2005: Engines are not evil but distracting 2009: Engines are the future! (emphasis mine)

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Russian Doll Pattern • Y. Katz, C. Lerche
 RailsConf 2009
 http://vimeo.com/4611379 • Build reusable slices not core to your app and embed it • Apps within apps • Implemented earlier as
 Merb slices http://www.flickr.com/photos/johnkay/3539939004

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http://www.flickr.com/photos/icebone/2876059462 Full Engines

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Full Engine $ rails plugin new \
 name --full A reusable app that fully integrates into your app MVC, routes, assets, etc defined in the engine are automatically available in your app http://www.flickr.com/photos/scania/2869106546

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Beware of Collisions

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Full engines 2005 2007 Rails 2.0 2009 Rails 2.3 2010 Rails 3.0 Engine concept introduced Railties Overhauled

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Railties http://www.flickr.com/photos/perry-pics/7721695188

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Railtie Power • Add rake tasks • Add generators • Hook into the Rails console load • Hook into the various Rails lifecycle events (before/after_initialize, to_prepare, etc) https://blog.engineyard.com/2010/extending-rails-3-with-railties

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# See Railtie::Configuration config.to_prepare { ... } module Awesome end class Railtie < Rails::Railtie end rake_tasks do load ‘/awesome.tasks’ end initializer ‘awesome.configure’ do |app| # do awesome things like # subscribe to ActiveSupport::Notifications end Creating a Railtie

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•# Called before the app’s config is loaded config.before_configuration = {...} •# Called before Rails has been initialized config.before_initialize = {...} •# Called before app classes are loaded config.before_eager_load = {...} Railtie Initializer Hooks

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•# Called after app classes are loaded config.to_prepare = {...} •# Called after Rails has been initialized config.after_initialize = {...} Railtie Initializer Hooks (cont)

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Using a Railtie # Gemfile of your app gem ‘awesome’, ’~> 1.0’ # awesome.gem # awesome/lib/awesome.rb require ‘awesome/railtie’ if defined?(Rails)

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How are Railties Discovered? class Railtie autoload :Configuration, "rails/railtie/configuration" include Initializable ABSTRACT_RAILTIES = %w(Rails::Railtie Rails::Engine Rails::Application) class << self private :new delegate :config, to: :instance def subclasses @subclasses ||= [] end def inherited(base) unless base.abstract_railtie? subclasses << base end end

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How are Railties Discovered? class Railtie autoload :Configuration, "rails/railtie/configuration" include Initializable ABSTRACT_RAILTIES = %w(Rails::Railtie Rails::Engine Rails::Application) class << self private :new delegate :config, to: :instance def subclasses @subclasses ||= [] end def inherited(base) unless base.abstract_railtie? subclasses << base end end def subclasses @subclasses ||= [] end def inherited(base) unless base.abstract_railtie? subclasses << base end end

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class Railtie The core API that all of Rails is built upon class ActionMailer::Railtie
 class ActionController::Railtie
 class ActionDispatch::Railtie
 ...
 class ActiveModel::Railtie
 class ActiveRecord::Railtie
 class ActiveSupport::Railtie If Rails can dogfood their own APIs to create Rails,
 chances are you can build awesome things too.

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Extending with Railties class Engine < Railtie class Application < Engine class Plugin < Engine

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Full engines Overhauled Railties 2005 2011 Rails 3.1 2007 Rails 2.0 2009 Rails 2.3 2010 Rails 3.0 Engine concept introduced Mountable engines

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Mountable Engines http://www.flickr.com/photos/granada_turnier/5818853700

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Mountable Engine $ rails plugin new \
 name --mountable Like full engines, but... --Namespaced --Routes must be mounted in your app http://www.flickr.com/photos/tshearer/3935429228

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Isolation via Namespacing

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Full vs Mountable> Defining # defining full engines class Engine < ::Rails::Engine end

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module Blog end # defining mountable engines isolate_namespace Blog class Engine < ::Rails::Engine end Full vs Mountable> Defining

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Full vs Mountable> Application Controller # Mountable engines define their # own ApplicationController module Blog class ApplicationController < ActionController::Base end

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Full vs Mountable> Routes # Full engine routes Rails.application.routes.draw do resources :posts end

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Blog::Engine.routes.draw do resources :posts end Rails.application.routes.draw do mount Blog::Engine => ‘/blog’ end # Mountable engine routes Full vs Mountable> Routes

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Full Mountable App ✔ ✔ Namespaced ✔ Routes Engines: Full vs Mountable Recap Inherited
 by your app Must be
 mounted

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http://www.paleofuture.com/blog/2007/4/24/postcards-show-the-year-2000-circa-1900.html Full+Mountable Engine?

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Full + Mountable Engine # Start with a mountable engine $ rails plugin new \ name --mountable

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Full + Mountable Engine (cont) # Draw routes into the main app # like a full engine # Caution: Beware of collisions! Rails.application.routes.draw do resources :posts end

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Mountable engines Full engines Overhauled Railties 2005 2012 Rails 3.2 2011 Rails 3.1 2007 Rails 2.0 2009 Rails 2.3 2010 Rails 3.0 Engine concept introduced vendor/plugins deprecated

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Mountable engines Full engines Overhauled Railties vendor/plugins deprecated 2005 2012 Rails 3.2 2011 Rails 3.1 2013 Rails 4.0 2007 Rails 2.0 2009 Rails 2.3 2010 Rails 3.0 Engine concept introduced Plugin removed

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git rm plugin.rb

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git rm plugin.rb

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Testing Engines http://www.flickr.com/photos/kwl/4809326028

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Dummy App • Full and Mountable engines are tested the same • A full blown dummy app is generated in /test which consumes your engine • Write tests against the dummy app http://www.flickr.com/photos/20759665@N03/7400887540

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$ gem install combustion http://www.flickr.com/photos/ekilby/4877912932

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When do you create an Engine? http://www.flickr.com/photos/m0php/530526644

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http://www.flickr.com/photos/limebye/3775235515 Start with a Monorail

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http://www.flickr.com/photos/wwwuppertal/6891421635 Refactor out engines only when you find commonality and duplication

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thank you. @kpshek