Ruby on Rails Routing Concerns
Example
To avoid repetition in nested routes, concerns provide a great way of sharing common resources that are reusable. To create a concern use the method concern within the routes.rb file. The method expects a symbol and block:
concern :commentable do
resources :comments
end
While not creating any routes itself, this code allows using the :concerns attribute on a resource. The simplest example would be:
resource :page, concerns: :commentable
The equivalent nested resource would look like this:
resource :page do
resource :comments
end
This would build, for example, the following routes:
/pages/#{page_id}/comments
/pages/#{page_id}/comments/#{comment_id}
For concerns to be meaningful, there must be multiple resources that utilize the concern. Additional resources could use any of the following syntax to call the concern:
resource :post, concerns: %i(commentable)
resource :blog do
concerns :commentable
end
