请查看：inverse_of 选项> 属于 和 has_many 。在不同情况下构建和获取关联记录时，此选项将处理双向分配。

Please look into the :inverse_of option for belongs_to and has_many. This option will handle two-way assignments when building and fetching associated records in different cases.

来自双向关联，用于 ActiveRecord :: Associations :: ClassMethods 在文档中：

在关联上指定：inverse_of 选项可让您告诉Active Record逆关系，它将优化对象加载。

Specifying the :inverse_of option on associations lets you tell Active Record about inverse relationships and it will optimise object loading.