Question

首先，我知道inverse_of在has_many关联中是如何工作的。

# relationship without inverse_of
user has_many :orders

# this will generate two database queries
user.orders.first.user
Order Load (0.1ms)  SELECT  `orders`.* FROM `orders` WHERE `orders`.`user_id` = 2  ORDER BY `orders`.`id` ASC LIMIT 1
User Load (0.1ms)  SELECT  `users`.* FROM `users` WHERE `users`.`id` = 2 LIMIT 1

这里，user和user.order.first.user是两个不同的对象。

并使用inverse_of

# relationship with inverse_of
user has_many :orders, inverse_of: :user

# this will generate just one database query
user.orders.first.user
Order Load (0.1ms)  SELECT  `orders`.* FROM `orders` WHERE `orders`.`user_id` = 2  ORDER BY `orders`.`id` ASC LIMIT 1

现在，user和user.order.first.user是同一个对象。

但是，这个belongs_to关联中有什么inverse_of呢？

# relationship with inverse_of in belongs_to association
order belongs_to :user, inverse_of: :orders

order.user.orders
# will generate two database queries
User Load (0.5ms)  SELECT  `users`.* FROM `users` WHERE `users`.`id` = 2 LIMIT 1
Order Load (0.1ms)  SELECT `orders`.* FROM `orders` WHERE `orders`.`user_id` = 2

如果我在此关系中使用inverse_of或不使用inverse_of，则没有区别。那么，也许我以错误的方式使用它？在belongs_to关联中，inverse_of的重点是什么？

Answer 1

本文帮助我理解:inverse_of选项 https://www.viget.com/articles/exploring-the-inverse-of-option-on-rails-model-associations

这个SO答案也可能有用：https://stackoverflow.com/a/9297745/6266499

在Rails belongs_to关联中inverse_of做了什么？

1 个答案: