Rails Best Practices: Routing Concerns in Rails 4

routes.rb

# Routing Concerns is an attempt to DRY up your config/routes.rb.
# The basic idea is to define common sub-resources (like comments)
# as concerns and include them in other resources/routes.
# Here’s the obvious example:

concern :commentable do
  resources :comments
end
 
concern :remarkable do
  resources :remarks
end
 
resources :posts, :concerns => :commentable 
resources :articles, :concerns => [:commentable, :remarkable] # can include several  

# The above is equivalent to the following Rails 3 code:

resources :posts do
  resources :comments
end
 
resources :articles do
  resources :comments
  resources :remarks
end

# source: http://net.tutsplus.com/tutorials/ruby/digging-into-rails-4/