不能DUP NilClass

Question

可能重複：
Rails - Cannot dup NilClass when using Single Table Inheritance

嗨，大家好，

我使用Rails 2.3.8和在Windows下的Ruby 1.8.7（是的，我知道我應該使用Linux ...現在沒有時間這樣做= P）

我正在嘗試製作一個簡單的STI模型。

我在哪裏有一個類User和一個繼承自User的子類（BusinessContact）。

我可以叫User.new，User.create和它得到保存在數據庫中，但是當我試圖BusinessContact.new或.create我得到：

can't dup NilClass 

D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2219:in `dup' 
D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2219:in `scoped_methods' 
D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2223:in `current_scoped_methods' 
D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2206:in `scoped?' 
D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2474:in `send' 
D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2474:in `initialize' 
D:/Users/Administrator/Projects/Addcamon/src/app/controllers/debug_controller.rb:3:in `new' 
D:/Users/Administrator/Projects/Addcamon/src/app/controllers/debug_controller.rb:3:in `index' 

用戶遷移創建如下：

# Create Users Table 
    create_table :users do |t| 
     t.string :type 

     # common attributes 
     t.string :login, :limit => 40 
     t.string :identity_url  
     t.string :name, :limit => 100, :default => '', :null => true 
     t.string :email, :limit => 100 
     t.string :crypted_password, :limit => 40 
     t.string :salt, :limit => 40 
     t.string :remember_token, :limit => 40 
     t.string :activation_code, :limit => 40 
     t.string :state, :null => :false, :default => 'passive'  
     t.datetime :remember_token_expires_at 
     t.string :password_reset_code, :default => nil 
     t.datetime :activated_at 
     t.datetime :deleted_at 
     t.timestamps 
    end 

我的模型是這樣定義的：

class User < ActiveRecord::Base 
    unloadable #I've added this cause I read somewhere it could fix the problem, but it didn't 
    include Authentication 
    include Authentication::ByPassword 
    include Authentication::ByCookieToken 
    include Authorization::AasmRoles 

    # Validations 
    validates_presence_of :login, :if => :not_using_openid? 
    validates_length_of :login, :within => 3..40, :if => :not_using_openid? 
    validates_uniqueness_of :login, :case_sensitive => false, :if => :not_using_openid? 
    validates_format_of :login, :with => RE_LOGIN_OK, :message => MSG_LOGIN_BAD, :if => :not_using_openid? 
    validates_format_of :name, :with => RE_NAME_OK, :message => MSG_NAME_BAD, :allow_nil => true 
    validates_length_of :name, :maximum => 100 
    validates_presence_of :email, :if => :not_using_openid? 
    validates_length_of :email, :within => 6..100, :if => :not_using_openid? 
    validates_uniqueness_of :email, :case_sensitive => false, :if => :not_using_openid? 
    validates_format_of :email, :with => RE_EMAIL_OK, :message => MSG_EMAIL_BAD, :if => :not_using_openid? 
    validates_uniqueness_of :identity_url, :unless => :not_using_openid? 
    validate :normalize_identity_url 
end 

class BusinessContact < User 

end 

心中已經Ë已經嘗試過卸載的解決方案，我見過的地方

我已經通過軌道控制檯試過，沒有運氣或者：

user = BusinessContact.new 
TypeError: can't dup NilClass 
     from D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2219:in `dup' 
     from D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2219:in `scoped_methods' 
     from D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2223:in `current_scoped_methods' 
     from D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2206:in `scoped?' 
     from D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2474:in `send' 
     from D:/Ruby187/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2474:in `initialize' 
     from (irb):9:in `new' 
     from (irb):9 

Answer 1

你定義裏面user.rb的BusinessContact類？如果是這樣，請嘗試移動到business_contact.rb，看看是否有幫助。