Rails-使用ActiveRecord进行深度嵌套连接

Question

我偶尔需要在我的应用程序中进行跨多个表的联接，但还没有完全弄清楚如何对3个以上的表进行联接：

class Store < ApplicationRecord
has_many :products
end
class Product < ApplicationRecord
belongs_to :store
has_many :product_variants
end
class ProductVariant < ApplicationRecord
belongs_to :product
has_many :order_list_items
end
class OrderListItem < ApplicationRecord
belongs_to :product_variant
has_many :consumers
end
class Consumer < ApplicationRecord
belongs_to :order_list_item
end

目前我已经准备好了：

Store.joins(products: [{ product_variants: :order_list_items }])

我现在想做的是加入每一个属于OrderListItem的消费者。

然而，当我尝试以下内容时：

Store.joins(products: [{ product_variants: :order_list_items }], order_list_items: [:consumers])

我得到错误：

(Object doesn't support #inspect)

以下两次尝试也会出现相同的错误：

Store.joins(products: [{ product_variants: :order_list_items }, order_list_items: [:consumers]])

Store.joins(products: [{ product_variants: :order_list_items }], order_list_items: [:consumers])

我已经正确设置了关联，并且order_list_item.consumers和consumer.order_list_items、order_list_item.product_variant以及product_variant.order_list_items工作良好。

我也没有在任何型号上覆盖initialize。

工作的SQL如下所示：

SELECT stores.id, products.id as product_id, product_variants.id as product_variant_id, order_list_items.id as list_item_id, consumers.id as consumer_id
FROM stores
INNER JOIN products ON products.store_id = stores.id
INNER JOIN product_variants on product_variants.product_id = products.id
INNER JOIN order_list_items on order_list_items.product_variant_id = product_variants.id
INNER JOIN consumers on consumers.order_list_item_id = order_list_items.id;

谢谢你的提示。

Answer 1

试试这个

Store.joins(products: [product_variants: [order_list_items: :consumers]])

下面是sql查询

SELECT "stores".* FROM "stores" 
INNER JOIN "products" 
ON "products"."store_id" = "stores"."id" 
INNER JOIN "product_variants" 
ON "product_variants"."product_id" = "products"."id" 
INNER JOIN "order_list_items" 
ON "order_list_items"."product_variant_id" = "product_variants"."id" 
INNER JOIN "consumers" 
ON "consumers"."order_list_item_id" = "order_list_items"."id";