2. Routing - 2.5 Scoping Routing Rules

2.5 Scoping Routing Rules

Rails gives you a variety of ways to bundle together related routing rules concisely. They’re all based on usage of the scope method and its various shortcuts.

get 'auctions/new' => 'auctions#new' 
get 'auctions/edit/:id' => 'auctions#edit' 
post 'auctions/pause/:id' => 'auctions#pause'

# Can Dry up with the scope method
scope controller: :auctions do
  get 'auctions/new' => :new
  get 'auctions/edit/:id' => :edit post 'auctions/pause/:id' => :pause
end

# DRY it up by adding the :path argument to scope
scope path: '/auctions', controller: :auctions do 
  get 'new' => :new
  get 'edit/:id' => :edit
  post 'pause/:id' => :pause
end

2.5.1 Controller

The scope method accepts a :controller option (or it can interpret a symbol as its first argument to assume a controller).

scope controller: :auctions do
scope :auctions do

# to make it obvious, use the controller method instead of scope
controller :auction do

2.5.2 Path Prefix

The scope method accepts a :path option (or it can interpret a string as its first parameter to mean a path prefix).

scope path: '/auction' do
scope 'auction' do

# in Rails 4, pass the :path option symbols instead of strings
scope :acutions, :archived do
# cope all routes nested under it to the “/auctions/archived” path.

2.5.3 Name Prefix

The scope method also accepts a :as option that affects the way that named route URL helper methods are generated.

# will generate a named URL helper method called admin_new_auction_url
scope :auctions, as: 'admin' do
  get 'new' => :new, as: 'new_auction'
end

2.5.4 Namespaces

URLs can be grouped by using the namespace method, which is syntactic sugar that rolls up module, name prefix and path prefix settings into one declaration. The implementation of the namespace method converts its first argument into a string, which is why in some example code you’ll see it take a symbol.

namespace :auctions, :controller => :auctions do 
  get 'new' => :new
  get 'edit/:id' => :edit
  post 'pause/:id' => :pause
end

2.5.5 Bundling Contraints

If you find yourself repeating similar segment key constraints in related routes, you can bundle them together using the :constraints option of the scope method:

# It’s likely that only a subset of rules in a given scope need constraints applied to them. 
scope controller: :auctions, constraints: {:id => /\d+/ } do 
  get 'edit/:id' => :edit
  post 'pause/:id' => :pause
end


scope path: '/auctions', controller: :auctions do 
  get 'new' => :new
  constraints id: /\d+/ do
    get 'edit/:id' => :edit
    post 'pause/:id' => :pause 
  end
end

To enable modular reuse, you may supply the constraints method with an object that has a matches? method.

class DateFormatConstraint 
  def self.matches?(request)
    request.params[:date] =~ /\A\d{4}-\d\d-\d\d\z/ # YYYY-MM-DD 
  end
end

# in routes.rb
constraints(DateFormatConstraint) do 
  get 'since/:date' => :since
end