My talk at Ruby Meetup Hamburg, January 10, 2018 19:00 hosted by XING (www.xing.com) Dammtorstrasse 29-32, 20354 Hamburg by Description: When a monolithic Rails app reaches a certain complexity, it becomes hard to understand what each part of code does. In this talk, I explained how to build a large rails app modularized by engines to enforce an internal dependency structure.

1. Rails Engines
By Gharbi Mohammed
Software Engineer at Event Inc
github.com/mgharbik
mgharbik@gmail.com

2. ● What problems one can face using monolithic rails app?
● How we could solve them by using:
○ Namespaces
○ Rails Engines
Content

3. Monolithic Rails App

4. Solution?

5. Namespaces
Modularity
Dependency structure

6. Engines

7. Engines

8. Engines

9. "The secret to building large apps is never build large
apps.

10. "The secret to building large apps is never build large
apps.
Break your applications into small pieces. Then,
assemble those testable, bite-sized pieces into your
big application"
- Justin Meyer

11. path 'components' do
gem 'content'
gem 'public_ui'
gem 'admin_ui'
gem 'api'
...
end
Gemfile

12. Rails.application.routes.draw do
mount PublicUi::Engine, at: '/'
mount AdminUi::Engine, at: '/admin'
mount Api::Engine, at: '/api'
...
end
Routes

13. ● each component in isolation
● dummy app
● spec_helper.rb
require File.expand_path("../dummy/config/environment", __FILE__)
Tests

14. #!/bin/bash
exit_code=0
echo "*** Running engine_name engine specs"
bundle install | grep Installing
RAILS_ENV=test bundle exec rake db:create
RAILS_ENV=test bundle exec rake db:migrate
bundle exec rspec spec
exit_code+=$?
exit $exit_code
test.sh

15. #!/bin/bash
result=0
cd "$( dirname "${BASH_SOURCE[0]}" )"
for test_script in $(find . -name test.sh); do
pushd `dirname $test_script` > /dev/null
./test.sh
result+=$?
popd > /dev/null
done
if [ $result -eq 0 ]; then
echo "SUCCESS"
else
echo "FAILURE"
fi
exit $result
build.sh

16. Benefits
● Component based architecture is complementary to good object oriented
practices
● Engines use namespaces
● It enforces an internal dependency structure
● Clean Gemfile
● Clean routes.rb
● Fast tests
● Working in large team

17. content
shared_ui
admin_ui public_ui
auth_ui registration_ui
api
importer user
search

18. content
shared_ui
admin_ui public_ui
auth_ui registration_ui
api
importer user
search

19. content
shared_ui
admin_ui public_ui
auth_ui registration_ui
api
importer user
search

20. ● https://github.com/plataformatec/devise
● https://github.com/solidusio/solidus
Examples

21. https://github.com/mgharbik/sportsball-cbra
Repo

22. Thank you

23. ● http://teotti.com/component-based-rails-architecture-primer
● http://tech.taskrabbit.com/blog/2014/02/11/rails-4-engines
● https://leanpub.com/cbra
Resources

24. $ rails plugin new admin_ui --mountable
Engine

25. initializer :append_migrations do |app|
unless app.root.to_s.match root.to_s+File::SEPARATOR
config.paths['db/migrate'].expanded.each do |expanded_path|
app.config.paths['db/migrate'] << expanded_path
end
end
end
Migrations

26. $ bundle exec rake engine_name:install:migrations
Migrations