Rails 管理中的 ActiveRecord::HasManyThroughNestedAssociationsAreReadonly 错误

Question

我刚刚升级到Rails 3.2.10并收到一条错误消息，这是我在通过 RailsAdmin 更新记录时从未收到过的。

ActiveRecord::HasManyThroughNestedAssociationsAreReadonly at /admin/vendor/12/edit

Message Cannot modify association 'Vendor#categories' because it goes through more than one other association.

这是我的Vendor模型：

class Vendor < ActiveRecord::Base
  attr_accessible :name, :description, :banner_image, :logo_image, :intro_text, :thumb_image, :category_ids, :product_ids, :user_id, :remove_banner_image, :banner_image_cache, :remove_logo_image, :logo_image_cache
    mount_uploader :banner_image, ImageUploader
    mount_uploader :logo_image, ImageUploader
    mount_uploader :thumb_image, ImageUploader

    has_many :products, :dependent => :destroy
    has_many :categories, :through => :products
    belongs_to :owner, :class_name => "User",
        :foreign_key => "user_id"   
end

这是我的Category模型：

class Category < ActiveRecord::Base
  attr_accessible :name, :product_ids, :category_ids
    has_many :category_products do
         def with_products
           includes(:product)
         end
       end

  has_many :products, :through => :category_products

end

这是我的Product模型：

class Product < ActiveRecord::Base
  attr_accessible :name, :description, :price, :vendor_id, :image, :category_ids, :sku, :remove_image, :image_cache
    mount_uploader :image, ImageUploader

    belongs_to :vendor
    has_many :category_products do
           def with_categories
             includes(:category)
           end
    end

    has_many :categories, :through => :category_products

end

这是我的CategoryProduct模型：

class CategoryProduct < ActiveRecord::Base
  attr_accessible :product_id, :category_id, :purchases_count

    belongs_to :product
  belongs_to :category

  validates_uniqueness_of :product_id, :scope => :category_id
end

Answer 1

发生这种情况是因为您的关联是嵌套的，这意味着（来自 Rails 源代码）：\n如果存在多个连接表，则贯穿关联是嵌套的...这就是您的情况。

\n\n

显然，一种解决方法（我没有测试）是告诉供应商它不需要自动保存关联。

\n\n

has_many :categories, :through => :products, :autosave => false\n

\n