Mountable Engines - Lonestar Ruby 2012

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Mountable Engines Playing well with other apps Patrick Peak @peakpg

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About Me

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The Problem: Reuse is hard

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Duplication is the root of all evil.

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Start with a Library

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Plugins

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Generated code makes upgrades costly

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Agenda • Why I care about Engines • What are they? • Building one • Learning to conﬁgure • Making installation easy • Using the Asset Pipeline • Working with other Engines

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Evolution of a CMS 2.3 3.0 Engines Introduced 3.1 Mountable Initializers Asset Pipeline 3.2

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What are Engines? Responsibilities: •  Business Domain •  Selling Stuff •  Managing Users •  Blogging App #2

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Separation of Concerns Selling Stuff Managing Users Blogging Business Domain App #2

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Examples Popular Engines

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E-commerce

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Authentication

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Admin Dashboards

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Building an Engine

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What the world needs… $ rails plugin new another --mountable

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Result: A Gem with a Rails App inside Rails App Gem

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Add a Resource $ rails g resource Page name path content

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‘Typical’ Controller

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Isolated Controller

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Isolated Namespace

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Routing Engines own their Routes

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Engine Routes Rails.application.routes.draw

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Our Awesome UI

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Mounting the Engine App Root

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Route Helpers <%= main_app.root_url %> # => / <%= another.root_url %> # => /another <%= another.page_path(@page) %> # => /another/pages/1

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Get Smarter

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Inside the Engine

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In your App

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Department of Redundancy Department…

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Migrations Sharing Structure across Projects

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Namespaced Tables

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From Gem to Project $ rake another:install:migrations • Copies all ﬁles from db/migrate into a project • Won’t overwrite • Retimestamps

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After installing 2 1

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For multiple engines $ rake railties:install:migrations

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Conﬁguratin’ Provide Reasonable Defaults

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http://edgeguides.rubyonrails.org/conﬁguring.html

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Initializers

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Adding behavior to Rails

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Middleware Stack

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“Suggested” Generators

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Make your engine conﬁgurable

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Be Nice Make life easy for new users

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Write a Readme gem "another" $ bundle install $ rake another:install:migrations $ rake db:migrate mount Another::Engine => "/another"

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Improve Installation gem "another” $ rail g another:install

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Generators

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Asset Pipeline Packaging the view

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Before /public $ rake copy:assets

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After Project gem "ckeditor_rails", "3.6.2.2"

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My Favorite Key

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Working Together Ups and Downs of multiple engines

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Common stacks are ok My Site BrowerCMS News Blog

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Conventions $ rails g cms:install bcms_news

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Common Installer

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The vision Your Engine Rails Admin

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Challenges A. Incompatible dependencies B. Rails has no common security model C. Mismatched user interfaces

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A. Incompatible Dependencies Devise =2.1.1 ~>2.0.0

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Solving Dependencies • Minimize dependencies • Follow rational versioning policy: o  Rubygems ‘recommended’ o  Major.Minor.Build (i.e. 3.5.4) §  Major – Backwards incompatible §  Minor – Backwards compatible, new features §  Build – Backwards compatible, details • Robustness Principle – Be liberal in what you accept o  ~> 2.0 better than ~>2.0.0

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B. No common security model Your App Restful Auth Devise current_user?

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Authentication Who are you, really?

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Authorization Are you allowed to do that?

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I don’t care, just pick something…

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C. Mismatched UIs

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Recap What I hope you learned

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Engines are the Future, and Awesome.

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Reduce errors from duplication

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When done right…

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The End Thanks! Feedback? @peakpg

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Attributions http://dilbert.com/strips/comic/2009-12-03/ http://trevorlibrarian.wordpress.com/2012/04/04/safety-first/ http://www.flickr.com/photos/rosenfeldmedia/4459977458/sizes/o/in/photostream/ https://www.ruby-toolbox.com/ http://www.flickr.com/photos/7571290@N05/440978769/sizes/m/in/photostream/ http://www.spreecommerce.com http://www.flickr.com/photos/verseguru/168920451/sizes/o/in/photostream/ http://www.flickr.com/photos/richardgiles/5284155911/sizes/o/in/photostream/ http://www.flickr.com/photos/museemccordmuseum/2918567169/sizes/o/in/photostream/ http://www.flickr.com/photos/whisperwolf/4487007569/