STI 多态 has_many 使用了错误的类型值

Question

我有以下 STI 模型，它们具有多态关联，其查询构造错误

class Product < ApplicationRecord
  has_many :images, as: :imageable
end

class OneProduct < Product
end

class Image < ApplicationRecord
  belongs_to :imageable
end

在 rails 控制台中，当我

> OneProduct.last.icon_images

正在触发的查询是

SELECT  * FROM images WHERE imageable_id = id AND imageable_type = 'Product'

我期待：

SELECT * from images WHERE imageable_id = id AND imageable_type = 'OneProduct'

我是不是有什么期待？

补充信息：数据库是 postgres。

Answer 1

来自 Rails 文档：

Using polymorphic associations in combination with single table inheritance (STI) is a little tricky. In order for the associations to work as expected, ensure that you store the base model for the STI models in the type column of the polymorphic association. To continue with the asset example above, suppose there are guest posts and member posts that use the posts table for STI. In this case, there must be a type column in the posts table.

Note: The attachable_type= method is being called when assigning an attachable. The class_name of the attachable is passed as a String.
class Asset < ActiveRecord::Base   
  belongs_to :attachable, polymorphic: true

  def attachable_type=(class_name)
     super(class_name.constantize.base_class.to_s)   
  end 
end

class Post < ActiveRecord::Base   
  # because we store "Post" in attachable_type now dependent: :destroy will work   
  has_many :assets,as: :attachable, dependent: :destroy 
end

class GuestPost < Post end

class MemberPost < Post end

来源： https://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#label-Polymorphic+Associations

所以它说，而不是存储 imageable_type = OneProduct 你只需要将它存储为 Product 并且你可以在 Product table。但这完全取决于您对 OneProduct 模型的需求，如果该模型上的 default_scope 可以在不添加 type 列的情况下为您工作，那么请不要将其添加到Product table 如果这不起作用，那么您可以添加该列，然后添加 default_scope 以在查询 OneProduct 模型时获取 products.type = OneProduct。

STI 多态 has_many 使用了错误的类型值

STI polymorphic has_many uses wrong type value

ruby-on-rails

polymorphic-associations