library consists of model extension, helpers, and views It was quite natural to implement as an Engine (Just wanted to try the new feature of Rails 3.0)
http://patshaughnessy.net/2011/9/10/ how-does-kaminari-paginate Active Record scopes vs class methods (Carlos Antônio) http://blog.plataformatec.com.br/ 2013/02/active-record-scopes-vs- class-methods/
namespaced models, controllers, views, etc. It can be "mounted" onto the parent Rails application's certain URL It can refer to the parent application from controllers / views via `main_app` method
#:nodoc: initializer 'erd' do |app| ActiveSupport.on_load(:after_initialize) do if Rails.env.development? Rails.application.routes.append do mount Erd::Engine, :at => '/erd' ennnnnnd
can edit current page like a Wiki page Catches URL missing in the browser for example, just visit http://localhost:3000/books Catches link_to missing in the browser for example, add `link_to 'authors', authors_path`