An intro to rails engines with practice labs.

1. COWBOYS & ENGINES
Fernand Galiana
Tuesday, September 17, 13

2. HISTORY
0.14.2 ~ 2005
2.3 ~ 2009 -- Engine support
3.0 ~ 2010 --Yehuda and crew
Tuesday, September 17, 13

3. SURPRISE?
> rails c
> Rails::Application.ancestors
=> [Rails::Application, Rails::Engine,...]
Tuesday, September 17, 13

4. IMPETUS?
Mini rails apps [MVC|Assets|lib]
Divide conquer
Reusable components
Decoupling
Performance
Tuesday, September 17, 13

5. ENGINE TYPES
full
mountable
Tuesday, September 17, 13

6. CREATE!
> rails plugin new engines/blee [opts]
Tuesday, September 17, 13

7. NOTABLES...
--full
--mountable
-T
-B
-d [mysql|pg|sqlite3|etc...]
-j [jquery|coffeescript]
-dummy_path
Tuesday, September 17, 13

8. CREATE!
> rails plugin new engines/cowboy
--mountable -T -B
--dummy-path=spec/dummy
-j coffeescript -d mysql
Tuesday, September 17, 13

9. TEH BROG!
You rock, bro!
Tuesday, September 17, 13

10. LAB I
git clone https://github.com/derailed/ng_training
git checkout -b lab_1
follow the README!
Tuesday, September 17, 13

11. ANATOMY
Tuesday, September 17, 13

12. STRUCTURE
cowboy_engine
o app
o bin
o config
o lib
o spec
Tuesday, September 17, 13

13. STRUCTURE
cowboy_engine
o app
o assets
o controllers
o helpers
o models
o views
o bin
o ...
Tuesday, September 17, 13

14. STRUCTURE
cowboy_engine
o app
o controllers
o cowboy_engine
o cowboys_controller.rb
o ...
o bin
o ...
Tuesday, September 17, 13

15. ENGINE GEMSPEC
Gem::Specification.new do |s|
s.name = "pilgrim"
s.version = Pilgrim::VERSION
s.authors = ["Fernand"]
s.email = ["fernand.galiana@gmail.com"]
s.homepage = "http://pilgrim"
s.summary = "Pilgrim’s engine"
s.description = "Pilgrim’s engine"
s.files = Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.rdoc"]
s.add_dependency 'rails' , '~> 4.0.0'
s.add_dependency 'bootstrap-sass' , '~> 2.3.2.2'
s.add_dependency 'font-awesome-sass-rails', '~> 3.0.2.2'
s.add_development_dependency "mysql2" , '~> 0.3.13'
s.add_development_dependency 'rspec-rails' , '~> 2.14.0'
end
Tuesday, September 17, 13

16. THE ENGINE
module Cowboy
class Engine < ::Rails::Engine
isolate_namespace
config.autoload_paths += [File.join( self.root, %w[lib blee] )]
end
end
Tuesday, September 17, 13

17. BUSINESS AS USUAL
rails g [model|controller|migration]
custom generators
engine initializers
Tuesday, September 17, 13

18. GEMFILE
gem ‘cowboy’, path:‘engines/cowboy’
my_app/Gemfile
Tuesday, September 17, 13

19. CONVENIENCE
Cowboy::Engine.root
Cowboy::Engine.helpers
Cowboy::Engine.routes.url_helpers
Tuesday, September 17, 13

20. MIGRATIONS
Tuesday, September 17, 13

21. MIGRATIONS
> rake cowboy:install:migrations
Tuesday, September 17, 13

22. MIGRATIONS
rake db:migrate SCOPE=Cowboy
Tuesday, September 17, 13

23. MONKEYMIGS!
module Cowboy
class Engine < ::Rails::Engine
isolate_namespace Cowboy
initializer :append_migrations do |app|
next if app.root.to_s.match self.root.to_s
config.paths["db/migrate"].expanded.each do |expanded_path|
app.config.paths["db/migrate"] << expanded_path
end
end
end
end
Tuesday, September 17, 13

24. ISOLATED MODELS
table names expects engine_name_table_name
self.table_name = :guns
or
table_name_prefix = “”
Tuesday, September 17, 13

25. ROUTING
Tuesday, September 17, 13

26. engines/cowboy/config/routes.rb
ENGINE ROUTES
Cowboy::Engine.routes.draw do
resources :guns, only: [:create]
resources :belt do
resources :ammos
end
end
Tuesday, September 17, 13

27. APP ROUTES
Rango::Application.routes.draw do
root 'welcome#index'
mount Cowboy::Engine => '/pilgrim', as: :cowboy_ng
resources :jenkins do
resources :bullets, controller: 'cowboy/bullets'
end
end
rango/config/routes.rb
Tuesday, September 17, 13

28. CONTEXT MATTERS!
Cowboy engine context
guns_path => /guns
main_app.welcome_path => /welcome
Main Application context
cowboy_ng.guns_path => /pilgrims/guns
welcome_path => /welcome
Tuesday, September 17, 13

29. my_app/controllers/guns_controller.rb
HELPERS
class GunsController < ApplicationController
helper Cowboy::BulletsHelper
...
end
Tuesday, September 17, 13

30. ENGINE ASSETS
stylesheet_link_tag cowboy/guns.css
javascript_include_tag cowboy/guns.js
or
*=require cowboy/guns
//=require cowboy/guns
Tuesday, September 17, 13

31. PARTIALS
render gun => render partial:‘cowboy/...’, object: gun
render :partial ‘fred’ => render :partial ‘cowboy/fred’
Tuesday, September 17, 13

32. LOADING ORDER
config.railties_order = [Cowboy::Engine, :main_app, :all]
Tuesday, September 17, 13

33. TESTING
Tuesday, September 17, 13

34. TESTING (RSPEC)
spec/dummy
Tuesday, September 17, 13

35. TESTING (RSPEC)
config.include Dummy::Application.routes.url_helpers
use_route :cowboy
Tuesday, September 17, 13

36. LAB II
Scenario: Other models in the system need to be
commentable. Spin out this functionality as a new
‘social’ engine
Tuesday, September 17, 13

37. CHEAT
> rails plugin new engines/social -T --mountable
-j coffeescript -B -d mysql
--dummy-path=spec/dummy
Tuesday, September 17, 13

38. LAB III
Scenario: PM wants a reporting admin ui to track
comments. In light of this new feature commenting
behavior needs to be shared across several engines.
Refactor social engine to depend on the new
common engine
Tuesday, September 17, 13

39. Q&A
Get a rope?
Tuesday, September 17, 13