This document discusses component-based architecture in Ruby on Rails applications. It describes how to break a Rails app into reusable Ruby gems called components or engines. Components can be tested and developed independently, then composed together through a shared dependency structure. This allows complexity to be managed by gradually introducing components as an app grows in size and scope.

1. component based Rails application
primer
Enrico Teotti -- @agenteo

2. component based Rails application
primer
Rogrido Teotti -- @agenteo

3. misconception that working on complex software
must feel hard

4. like carrying 200 potatos is harder than carrying 20

5. This is wrong for two reasons: software
development is knowledge work not labour and
because of documented patterns to tackle software
complexity with incremental code design

6. decorators, presenters, service objects can
be sufficient to handle some complexity but
when the project is over a certain size
they don’t help understand what the
whole application does

7. Component based architecture is complementary to
good object oriented practices and uses
namespaces, test driven development and Ruby
gems to gradually define application boundaries
and enforce an internal dependency structure.

8. path 'components' do
gem 'public_ui'
gem 'admin_ui'
gem 'legacy_migration'
end
intention revealing Gemfile

9. Component is the name given to a Ruby on Rails
engine or Ruby gem when used as building block of
the Rails application

10. ● are ruby gems
● are special ruby gems that provide extra
behaviour (models, views, routes, rake
tasks) to a Rails application
● they can be hosted on a gemserver or
they can live inside your repository
● can be tested in isolation
what are rails engines?

11. config/routes.rb
Rails.application.routes.draw do
case AppRunningMode.value
when :admin
mount AdminUi::Engine => "/"
when :public
mount PublicUi::Engine => "/"
else
mount AdminUi::Engine => "/"
mount PublicUi::Engine => "/"
end
end

12. don’t architect an application with components from
day one instead introduce them gradually as the
complexity grows or when the scope changes

13. RUNNING_MODE=public rails s
RUNNING_MODE=admin rails s
http://example-internal-vpn-domain.com/admin
http://example.com/content
rails s
http://localhost:3000

14. proceeding without automated tests
could drive you crazy

15. use the test dummy app

16. avoid high level engines coupling
admin_ui
public_ui

17. admin_ui public_ui
domain_logic

18. DomainLogic::Content::Article

19. admin_ui public_ui
shared_ui domain_logic

20. Gem::Specification.new do |s|
# ... other fields up here
s.name = "admin_ui"
s.add_dependency "rails", "~> 4.1.1"
s.add_dependency 'jquery-rails'
s.add_dependency 'mongoid'
s.add_dependency 'faraday'
s.add_dependency "domain_logic"
s.add_dependency "shared_ui"
s.add_development_dependency 'byebug'
s.add_development_dependency 'database_cleaner'
s.add_development_dependency 'rspec-rails', '2.99.0'
s.add_development_dependency 'vcr'
s.add_development_dependency 'webmock'
s.add_development_dependency 'capybara'
s.add_development_dependency 'poltergeist'
end
admin_ui/admin_ui.gemspec

21. admin_ui public_ui
shared_ui domain_logic
legacy data
import

22. admin_ui public_ui
shared_ui domain_logic
legacy data
import
global search

23. admin_ui/app/views/cargo_preview/show.html.erb
<%# admin console stuff here %>
<%= render partial: 'shared_ui/cargos/show' %>
<%# admin spaceship here %>
public_ui/app/views/cargos/show.html.erb
<%= render partial: 'shared_ui/cargos/show' %>

24. http://teotti.com
Enrico Teotti - @agenteo
http://teotti.com/component-based-rails-architecture-primer/
Questions?