.save 上的 Rails 参数错误 - 与模型中的 has_many belongs_to 有关答案

【问题标题】：Rails Argument Error on .save - Something to do with has_many belongs_to in Model.save 上的 Rails 参数错误 - 与模型中的 has_many belongs_to 有关
【发布时间】：2013-03-30 02:23:58
【问题描述】：

尝试将条目保存到我的数据库时出现以下错误：

ArgumentError: Unknown key: class

当我尝试定义我的Page 模型属于哪个PageIcon 时会发生这种情况。

页面迁移：

class CreatePages < ActiveRecord::Migration
  def change
    create_table :pages do |t|
      t.integer "parent_page_id"
      t.integer "page_image_id", :null => false
      t.integer "page_icon_id"
      t.integer "template_id"

      t.string "title", :null => false
      t.string "path", :default => "", :null => false
      t.string "group"
      t.datetime "deleted_at"
      t.boolean "visible", :default => false

      t.timestamps
    end
    add_index("pages", "parent_page_id")
    add_index("pages", "page_image_id")
    add_index("pages", "page_icon_id")
    add_index("pages", "template_id")
    add_index("pages", "title")
    add_index("pages", "path")
  end
end

页面模型：

class Page < ActiveRecord::Base
  belongs_to :parent, :class_name => 'Page', :foreign_key => 'parent_page_id'
  has_many :children, :class_name => 'Page', :foreign_key => 'parent_page_id'
  belongs_to :page_image, :class_name => 'Image', :foreign_key => 'page_image_id'
  has_many :sections
  has_many :attributes
  belongs_to :page_icon, :class_name => 'PageIcon', :foreign_key => 'page_icon_id'

  validates_uniqueness_of :title, :case_sensitive => false
end

PageIcon 迁移

class CreatePageIcons < ActiveRecord::Migration
  def change
    create_table :page_icons do |t|
      t.string 'title', :null => false
      t.string 'description'
      t.string 'url', :null => false
      t.timestamps
    end
  end
end

PageIcon 模型：

class PageIcon < ActiveRecord::Base
  has_many :pages, :class_name => 'Page', :foreign_key => 'page_icon_id'
end

当我在 Rails 控制台中输入以下内容时，出现错误：

p = Page.find(1)
p.page_icon = PageIcon.find(1)
p.save

错误： ArgumentError: Unknown key: class

完整日志：

1.9.3-p392 :001 > p = Page.find(4)
  Page Load (0.8ms)  SELECT `pages`.* FROM `pages` WHERE `pages`.`id` = 4 LIMIT 1
 => #<Page id: 4, parent_page_id: nil, page_image_id: 1, page_icon_id: nil, template_id: nil, title: "Food", path: "", group: nil, deleted_at: nil, visible: true, created_at: "2013-03-29 12:21:31", updated_at: "2013-03-29 12:21:31"> 
1.9.3-p392 :002 > p.page_icon = PageIcon.find(2)
  PageIcon Load (0.3ms)  SELECT `page_icons`.* FROM `page_icons` WHERE `page_icons`.`id` = 2 LIMIT 1
 => #<PageIcon id: 2, title: "Food", description: nil, url: "page_icons/food.svg", created_at: "2013-03-30 01:37:13", updated_at: "2013-03-30 01:37:13"> 
1.9.3-p392 :003 > p.save
   (0.2ms)  BEGIN
  Page Exists (0.5ms)  SELECT 1 AS one FROM `pages` WHERE (`pages`.`title` = 'Food' AND `pages`.`id` != 4) LIMIT 1
   (0.2ms)  ROLLBACK
ArgumentError: Unknown key: class
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activesupport-3.2.12/lib/active_support/core_ext/hash/keys.rb:51:in `block in assert_valid_keys'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activesupport-3.2.12/lib/active_support/core_ext/hash/keys.rb:50:in `each_key'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activesupport-3.2.12/lib/active_support/core_ext/hash/keys.rb:50:in `assert_valid_keys'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/associations/builder/association.rb:33:in `validate_options'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/associations/builder/association.rb:24:in `build'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/autosave_association.rb:139:in `build'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/associations/builder/belongs_to.rb:14:in `build'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/associations/builder/association.rb:12:in `build'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/associations.rb:1431:in `belongs_to'
    from /Users/RyanKing/Sites/gastromica/app/models/attribute.rb:3:in `<class:Attribute>'
    from /Users/RyanKing/Sites/gastromica/app/models/attribute.rb:1:in `<top (required)>'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activesupport-3.2.12/lib/active_support/dependencies.rb:469:in `load'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activesupport-3.2.12/lib/active_support/dependencies.rb:469:in `block in load_file'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activesupport-3.2.12/lib/active_support/dependencies.rb:639:in `new_constants_in'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activesupport-3.2.12/lib/active_support/dependencies.rb:468:in `load_file'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activesupport-3.2.12/lib/active_support/dependencies.rb:353:in `require_or_load'
... 35 levels...
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/validations.rb:50:in `save'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/attribute_methods/dirty.rb:22:in `save'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/transactions.rb:259:in `block (2 levels) in save'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/transactions.rb:313:in `block in with_transaction_returning_status'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/connection_adapters/abstract/database_statements.rb:192:in `transaction'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/transactions.rb:208:in `transaction'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/transactions.rb:311:in `with_transaction_returning_status'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/transactions.rb:259:in `block in save'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/transactions.rb:270:in `rollback_active_record_state!'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.12/lib/active_record/transactions.rb:258:in `save'
    from (irb):3
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.12/lib/rails/commands/console.rb:47:in `start'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.12/lib/rails/commands/console.rb:8:in `start'
    from /Users/RyanKing/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.12/lib/rails/commands.rb:41:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'1.9.3-p392 :004 >

当我删除 Page 和 PageIcons 模型之间的 has_many 和 belongs_to 关系时，一切正常。有谁知道这里发生了什么？据我所知语法是正确的。

更新

属性是rails中的保留字，如下所示：http://www.ruby-forum.com/topic/2722528

因此，在 Page 模型中将 has_many :attributes 更改为 has_many :page_attributes, class_name="Attribute" 就可以解决问题。

【问题讨论】：

我已经对此进行了测试，它似乎工作正常，所以我认为问题不在 Page 或 PageIcon 模型上。错误日志中提到了“/app/models/attribute.rb”——你在里面有什么？
谢谢我在 attributes.rb 中不小心写了 :call 而不是 :class_name - 我现在得到错误作为回报：undefined method keys' for []:ActiveRecord::Relation`
去吧！此处指出，属性是 rails 中的保留字：ruby-forum.com/topic/2722528 - 感谢您的帮助。

标签： ruby-on-rails model migration relational-database runtime-error

【解决方案1】：

属性是rails中的保留字，如下所示：http://www.ruby-forum.com/topic/2722528

因此，在 Page 模型中将 has_many :attributes 更改为 has_many :page_attributes, class_name="Attribute" 就可以解决问题。

【讨论】：

【解决方案2】：

我认为您根本不需要 :class_name 或 :foreign_key 哈希。你的关系是以标准方式建立的，所以这些哈希是多余的。

【讨论】：

是的，它们只是作为错误检查的结果而存在 - 否则错误仍然会发生。
唯一让我震惊的是任何模型上都没有attr_accessible。如果添加它们会发生什么？
不，attr_accessible 没有帮助，抱歉。