查询rails中的多级关联

Question

I have associations as below: Location Class

class Location < ActiveRecord::Base
  has_many :items
end

Item class

class Item < ActiveRecord::Base
  belongs_to :location
  belongs_to :category
end

Category class

class category < ActiveRecord::Base
  has_many :items
end

Now i want to query Location.categories (show all categories of location items). How can i achieve this?

Answer 1

It should be as simple as this:

class Location < ActiveRecord::Base
  has_many :items
  has_many :categories, :through => :items
end