Visualizando o relacionamento do modelo

brew install graphviz

group :development, :test do
    gem 'railroady'
end

uma maneira de usá-lo http://engineering.coachup.com/visualizing-rails-schemas-railroady-gem/

bundle install
railroady -o models.dot -M
dot -Tpng models.dot > models.png

outra maneira de usá-lo https://github.com/preston/railroady

rake diagram:all