麻烦简单的Rails嵌套关联where子句为父

Question

我有以下型号：

class Business < ApplicationRecord
  has_many :shopping_trips
end

class ShoppingTrip < ApplicationRecord
  belongs_to :business
  has_many :purchases
end

class Purchase < ApplicationRecord
  belongs_to :shopping_trip
end

因此，一个企业可以有很多购物之旅，每个购物之旅都可以有很多购物。

我试图在Purchase表上运行一个简单的查询来查找属于特定业务的购买。所以我写这个：

purchases = Purchase.joins(:shopping_trip => :business ).where(:shopping_trip => {:business_id => 1})

不幸的是它不起作用。我收到以下错误：

ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "shopping_trip"
LINE 1: ...sses"."id" = "shopping_trips"."business_id" WHERE "shopping_...
                                                             ^
: SELECT "purchases".* FROM "purchases" INNER JOIN "shopping_trips" ON "shopping_trips"."id" = "purchases"."shopping_trip_id" INNER JOIN "businesses" ON "businesses"."id" = "shopping_trips"."business_id" WHERE "shopping_trip"."business_id" = $1

连接看起来很正确，但where子句似乎失败了。

Answer 1

ActiveRecord :: StatementInvalid：PG :: UndefinedTable：ERROR：缺少表“shopping_trip”的FROM子句条目

您需要在where中指定表名而不是关联名。所以shopping_trip应该是shopping_trips

purchases = Purchase.joins(:shopping_trip => :business ).where(:shopping_trips => {:business_id => 1})

Answer 2

更好的解决方案是设置间接关联，以便您可以通过连接模型进行查询而无需手动连接：

class Business < ApplicationRecord
  has_many :shopping_trips
  has_many :purchases, through: :shopping_trips
end

class ShoppingTrip < ApplicationRecord
  belongs_to :business
  has_many :purchases
end

class Purchase < ApplicationRecord
  belongs_to :shopping_trip
  has_one :business, through: :shopping_trip
end

您现在可以从任何一方查询：

@business = Business.eager_load(:purchases).find(1)
@purchases = @business.purchases

# or
@purchases = Purchase.eager_load(:buisness).where(businesses: { id: 1 })

Answer 3

检查这...

all_purchase = Purchase.all

all_purchase.each do | each_purchase | each_purchase.shopping_trip.business结束