Creating Mountable Engines

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Creating Mountable Engines Patrick Peak @peakpg

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About me

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Problem: Repeating yourself is easy

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Duplication is the root of all evil.

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Start with a library

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Plugins are dead

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Generated code makes upgrades costly

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Engines are the solution

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Agenda Agenda • - Why I care • - How to make one • - Things you can do • - Working with others

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Evolving a CMS with engines Evolution of a CMS 3.0 Engines Introduced 3.1 -Mountable -Initializers -Asset Pipeline 4.0 2.3 Gems over plugins

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

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Separation of concerns 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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Creating an engine What the world needs… $ rails plugin new rubypress --mountable

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Result: A gem with a rails app inside Gemspec Rails App

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Add a resource Add a Resource $ rails g resource Page name path content

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The ‘expected’ controller ‘Typical’ Controller

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An isolated controller

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Isolated Namespace Deﬁning an isolated namespace

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Routing Engines own their routes

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Multiple buckets of controllers Application Engine #2 Engine #1

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Engine routes Engine Routes Rails.application.routes.draw

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Calling resources http://localhost:3000/rubypress/pages

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Mounting the engine App Root

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

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Getting smart about your routes

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A view from inside the engine

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Views inside your application

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An engine by any other name…

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Would be just as redundant

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Migrations Sharing structure across projects

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Namespaced tables Namespaced Tables

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Out of the gem, into the project From Gem to Project $ rake rubypress:install:migrations - Copies from gem’s db/migrate into a project - Won’t overwrite existing

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After installing 2 1 ####_create_rubypress_pages.rubypress.rb

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Installing migrations for all engines For multiple engines $ rake railties:install:migrations

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Conﬁguration Provide reasonable defaults

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

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Initializers Initializers

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Extending rails behavior

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Using new DSL

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Middleware stack

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“Suggested” generators “Suggested” Generators

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Make your engine conﬁgurable

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Overriding default conﬁguration

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Be Nice Make life easy for new users

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Write a README Write a Readme gem "rubypress" $ bundle install $ rake rubypress:install:migrations $ rake db:migrate mount Rubypress::Engine=>"/rubypress"

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Improve installation Improve Installation gem "rubypress" $ rail g rubypress:install

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Generators Generators

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Asset Pipeline Packaging the view

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Before 3.1 /public $ rake rubypress:copy_assets

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After 3.1 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 easier My Site BrowerCMS News Blog

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Allows for established conventions Establishing Conventions $ rails g cms:install bcms_news

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A common installer

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The Holy Grail for engine ecosystem The vision Your Engine Rails Admin

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Challenges on our quest 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 Rails Admin

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Managing your engine dependencies Solving Dependencies - Minimize dependencies - Be Rational: Major.Minor.Build (i.e. 3.5.4) - Major – Backwards incompatible - Minor – New features - Build – Details - Robustness Principle: - Be liberal in what you accept - ~> 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 which, just pick one…

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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!

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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/jowo/95371566/sizes/o/in/photostream/ 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/

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Questions?