如何通过关系使用has_many的命名关联？

Question

如何写这个：

has_many :sales, foreign_key: :buyer_id, dependent: :destroy
has_many :purchased_books, class_name: 'Book', through: :sales, source: :book 

这样：

has_many :purchases, class_name: 'Sale', foreign_key: :buyer_id, dependent: :destroy
has_many :purchased_books, class_name: 'Book', through: :sales, source: :book 

目前它给我以下错误：

Could not find the association :sales in model User (ActiveRecord::HasManyThroughAssociationNotFoundError)

编写has_many：当foreign_key :: buyer_id时，销售在语法上是不正确的。

Answer 1

：through键必须引用已定义的关联。

has_many :purchases, class_name: 'Sale', foreign_key: :buyer_id, dependent: :destroy
has_many :purchased_books, class_name: 'Book', through: :purchases, source: :book