Routing
Concerns
allow you to declare common routes that can be reused inside others resources and routes.
concern :commentable do
resources :comments
end
concern :image_attachable do
resources :images, only: :index
end
These concerns are used in Resources
routing:
resources :messages, concerns: [:commentable, :image_attachable]
or in a scope or namespace:
namespace :posts do
concerns :commentable
end
Instance Public methods
concern(name, callable = nil, &block) Link
Define a routing concern using a name.
Concerns
may be defined inline, using a block, or handled by another object, by passing that object as the second parameter.
The concern object, if supplied, should respond to call
, which will receive two parameters:
* The current mapper
* A hash of options which the concern object may use
Options may also be used by concerns defined in a block by accepting a block parameter. So, using a block, you might do something as simple as limit the actions available on certain resources, passing standard resource options through the concern:
concern :commentable do |options|
resources :comments, options
end
resources :posts, concerns: :commentable
resources :archived_posts do
# Don't allow comments on archived posts
concerns :commentable, only: [:index, :show]
end
Or, using a callable object, you might implement something more specific to your application, which would be out of place in your routes file.
# purchasable.rb
class Purchasable
def initialize(defaults = {})
@defaults = defaults
end
def call(mapper, options = {})
options = @defaults.merge(options)
mapper.resources :purchases
mapper.resources :receipts
mapper.resources :returns if options[:returnable]
end
end
# routes.rb
concern :purchasable, Purchasable.new(returnable: true)
resources :toys, concerns: :purchasable
resources :electronics, concerns: :purchasable
resources :pets do
concerns :purchasable, returnable: false
end
Any routing helpers can be used inside a concern. If using a callable, they’re accessible from the Mapper
that’s passed to call
.
concerns(*args) Link
Use the named concerns
resources :posts do
concerns :commentable
end
Concerns
also work in any routes helper that you want to use:
namespace :posts do
concerns :commentable
end
# File actionpack/lib/action_dispatch/routing/mapper.rb, line 2098 def concerns(*args) options = args.extract_options! args.flatten.each do |name| if concern = @concerns[name] concern.call(self, options) else raise ArgumentError, "No concern named #{name} was found!" end end end