ruby-on-rails - ActiveRecord::SubclassNotFound:单表继承机制未能定位子类

Question

我是 Rails 新手。
我有两个模型类别和产品，如下所示:-

class Category < ActiveRecord::Base
 attr_accessible :type

 has_many :products
end

class Product < ActiveRecord::Base
 attr_accessible :category_id, :color, :price, :title

 belongs_to :category
end

我的schema.rb如下:-

ActiveRecord::Schema.define(:version => 20130725220046) do

create_table "categories", :force => true do |t|
    t.string   "type"
    t.datetime "created_at", :null => false
    t.datetime "updated_at", :null => false
  end

  create_table "products", :force => true do |t|
    t.integer  "category_id"
    t.decimal  "price",       :precision => 10, :scale => 0
    t.string   "title"
    t.string   "color"
    t.datetime "created_at",                                 :null => false
    t.datetime "updated_at",                                 :null => false
  end

end

在 Rails 控制台中，我使用 Product.create 命令创建了两个产品，其中包含两个产品

[#<Product id: 1, category_id: 1, price: 500, title: "shirt", color: "blue", `created_at: "2013-07-25 22:04:54", updated_at: "2013-07-25 22:04:54">, #<Product id: 2, category_id: 1, price: 600, title: "tees", color: "black", created_at: "2013-07-25 22:05:17", updated_at: "2013-07-25 22:05:17">]`  

并使用控制台中的Category.create命令创建了两个类别

<Category id: 1, type: "clothing", created_at: "2013-07-25 22:03:54", updated_at: "2013-07-25 22:03:54"><Category id: 2, type: "footwear", created_at: "2013-07-25 22:04:02", updated_at: "2013-07-25 22:04:02">  

现在，Product.all 工作正常，但 Category.all 给出

ActiveRecord::SubclassNotFound: The single-table inheritance mechanism failed to locate the subclass: 'clothing'. This error is raised because the column 'type' is reserved for storing the class in case of inheritance. Please rename this column if you didn't intend it to be used for storing the inheritance class or overwrite Category.inheritance_column to use another column for that information.

这里面有什么问题吗？我想在类别和产品之间建立关系，例如
一个类别有_许多产品，并且产品属于_一个类别。

Answer 1

type 是受限词，您不能将其用作 ActiveRecord 模型中的列名称(除非您正在执行 STI)。