Module: FriendlyId::Scoped

Unique Slugs by Scope

The Scoped module allows FriendlyId to generate unique slugs within a scope.

This allows, for example, two restaurants in different cities to have the slug joes-diner:

class Restaurant < ActiveRecord::Base
  extend FriendlyId
  belongs_to :city
  friendly_id :name, :use => :scoped, :scope => :city
end

class City < ActiveRecord::Base
  extend FriendlyId
  has_many :restaurants
  friendly_id :name, :use => :slugged
end

City.find("seattle").restaurants.find("joes-diner")
City.find("chicago").restaurants.find("joes-diner")

Without :scoped in this case, one of the restaurants would have the slug joes-diner and the other would have joes-diner--2.

The value for the :scope option can be the name of a belongs_to relation, or a column.

Additionally, the :scope option can receive an array of scope values:

class Cuisine < ActiveRecord::Base
  extend FriendlyId
  has_many :restaurants
  friendly_id :name, :use => :slugged
end

class City < ActiveRecord::Base
  extend FriendlyId
  has_many :restaurants
  friendly_id :name, :use => :slugged
end

class Restaurant < ActiveRecord::Base
  extend FriendlyId
  belongs_to :city
  friendly_id :name, :use => :scoped, :scope => [:city, :cuisine]
end

All supplied values will be used to determine scope.

Finding Records by Friendly ID

If you are using scopes your friendly ids may not be unique, so a simple find like

Restaurant.find("joes-diner")

may return the wrong record. In these cases it's best to query through the relation:

@city.restaurants.find("joes-diner")

Alternatively, you could pass the scope value as a query parameter:

Restaurant.find("joes-diner").where(:city_id => @city.id)

Finding All Records That Match a Scoped ID

Query the slug column directly:

Restaurant.find_all_by_slug("joes-diner")

Routes for Scoped Models

Recall that FriendlyId is a database-centric library, and does not set up any routes for scoped models. You must do this yourself in your application. Here's an example of one way to set this up:

# in routes.rb
resources :cities do
  resources :restaurants
end

# in views
<%= link_to 'Show', [@city, @restaurant] %>

# in controllers
@city = City.find(params[:city_id])
@restaurant = @city.restaurants.find(params[:id])

# URLs:
http://example.org/cities/seattle/restaurants/joes-diner
http://example.org/cities/chicago/restaurants/joes-diner