ruby-on-rails - Rails 3 中的多态关联

Question

我想我快疯了。

假设我有 3 个模型:地址、仓库、类别:

class Address < ActiveRecord::Base
  belongs_to :category
  belongs_to :addressable, :polymorphic => true

  scope :billing_addresses , where(:categories => {:name => 'billing'}).joins(:category)  
  scope :shipping_addresses , where(:categories => {:name => 'shipping'}).joins(:category) 

end 


class Category < ActiveRecord::Base
  has_many :addresses
  has_many :subcategories, :class_name  => "Category", :foreign_key => "category_id"
  belongs_to :category, :class_name => "Category"  
end


class Warehouse < ActiveRecord::Base
  has_many :addresses, :as => :addressable
end

地址是多态的，因为最终我将使用它来存储客户、人员、员工等的地址。每个地址也可以是某种类型:账单、运输、工作、家庭等。

我正在尝试在页面上提取一些信息。

@some_warehouse = Warehouse.first

那么在我看来:

%b= @some_warehouse.name
%b= @some_warehouse.billing_address.address_line_1

等等。

我最终会查找每一行信息。

我试着做这样的事情

Warehouse.includes(:addresses).where(:name => "Ware1")
Warehouse.joins(:addresses).where(:name => "Ware1")

以及各种变化。
无论我做什么，我都无法让 rails 预加载所有表格。我究竟做错了什么？

Answer 1

以下是修改后的模型，它在 sql 中进行适当的连接并将查询数量从 16 减少到 8，每条信息一个，而不是也执行查找类别等的倍数:

class Address < ActiveRecord::Base
  belongs_to :category
  belongs_to :addressable, :polymorphic => true

  scope :billing_addresses ,  where(:categories => {:name => 'billing'}).includes(:category)
  scope :shipping_addresses , where(:categories => {:name => 'shipping'}).includes(:category)

end

class Warehouse < ActiveRecord::Base
  has_many :addresses,  :as => :addressable,  :include => :category, :dependent => :destroy

  def billing_address
    self.addresses.billing_addresses.first
  end    
  def shipping_address
    self.addresses.shipping_addresses.first
  end   
end


class Category < ActiveRecord::Base
  has_many :addresses
  has_many :subcategories, :class_name  => "Category", :foreign_key => "category_id"
  belongs_to :category, :class_name => "Category"  
end

sleep 有帮助。也不要忘记不时重新加载控制台:-)