ruby-on-rails – Rails：未定义的方法’to_sym’

NoMethodError(nil的未定义方法`to_sym’：NilClass)：

我使用Sqlite的应用程序的本地测试安装没有得到错误,但我部署的应用程序运行Mysql.两者之间的唯一区别是我在本地计算机上运行Ruby 1.8.7,在部署服务器上运行1.8.6.

我已经包含了User.rb中的代码和下面的错误日志.我在声明授权和嵌入式授权Railscast之后进行了设置.

任何帮助将不胜感激！

编辑：这是application_controller的代码,我使用before_filter设置current_user：

class ApplicationController < ActionController::Base
  helper :all
  helper_method :current_user_session,:current_user 
  before_filter :set_current_user

  protected 

  def set_current_user
    Authorization.current_user = current_user
  end

  def current_user_session  
    return @current_user_session if defined?(@current_user_session)  
    @current_user_session = UserSession.find  
  end  

  def current_user  
    @current_user = current_user_session && current_user_session.record  
  end
end

–

User.rb：

class User < ActiveRecord::Base
  acts_as_authentic 

  has_many :products
  has_many :transactions

  ROLES = %w[admin dmstaff staff faculty]

  def role_symbols
    [role.to_sym]
  end  

end

错误日志：

NoMethodError (undefined method `to_sym' for nil:NilClass):
  app/models/user.rb:10:in `role_symbols'
  /usr/lib/ruby/gems/1.8/gems/declarative_authorization 0.4/lib/declarative_authorization/authorization.rb:242:in `roles_for'
  /usr/lib/ruby/gems/1.8/gems/declarative_authorization-0.4/lib/declarative_authorization/authorization.rb:296:in  `user_roles_privleges_from_options'
  /usr/lib/ruby/gems/1.8/gems/declarative_authorization-0.4/lib/declarative_authorization/authorization.rb:161:in `permit!'
  /usr/lib/ruby/gems/1.8/gems/declarative_authorization-0.4/lib/declarative_authorization/in_controller.rb:580:in `permit!'
  /usr/lib/ruby/gems/1.8/gems/declarative_authorization-0.4/lib/declarative_authorization/in_controller.rb:109:in `filter_access_filter'
  /usr/lib/ruby/gems/1.8/gems/declarative_authorization-0.4/lib/declarative_authorization/in_controller.rb:109:in `each'
  /usr/lib/ruby/gems/1.8/gems/declarative_authorization-0.4/lib/declarative_authorization/in_controller.rb:109:in `all?'
  /usr/lib/ruby/gems/1.8/gems/declarative_authorization-0.4/lib/declarative_authorization/in_controller.rb:109:in `filter_access_filter'
  passenger (2.2.5) lib/phusion_passenger/rack/request_handler.rb:95:in `process_request'
  passenger (2.2.5) lib/phusion_passenger/abstract_request_handler.rb:207:in `main_loop'
  passenger (2.2.5) lib/phusion_passenger/railz/application_spawner.rb:378:in `start_request_handler'
  passenger (2.2.5) lib/phusion_passenger/railz/application_spawner.rb:336:in `handle_spawn_application'
  passenger (2.2.5) lib/phusion_passenger/utils.rb:183:in `safe_fork'
  passenger (2.2.5) lib/phusion_passenger/railz/application_spawner.rb:334:in `handle_spawn_application'
  passenger (2.2.5) lib/phusion_passenger/abstract_server.rb:352:in `__send__'
  passenger (2.2.5) lib/phusion_passenger/abstract_server.rb:352:in `main_loop'
  passenger (2.2.5) lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
  passenger (2.2.5) lib/phusion_passenger/abstract_server.rb:163:in `start'
  passenger (2.2.5) lib/phusion_passenger/railz/application_spawner.rb:213:in `start'
  passenger (2.2.5) lib/phusion_passenger/spawn_manager.rb:262:in `spawn_rails_application'
  passenger (2.2.5) lib/phusion_passenger/abstract_server_collection.rb:126:in `lookup_or_add'
  passenger (2.2.5) lib/phusion_passenger/spawn_manager.rb:256:in `spawn_rails_application'
  passenger (2.2.5) lib/phusion_passenger/abstract_server_collection.rb:80:in `synchronize'
  passenger (2.2.5) lib/phusion_passenger/abstract_server_collection.rb:79:in `synchronize'
  passenger (2.2.5) lib/phusion_passenger/spawn_manager.rb:255:in `spawn_rails_application'
  passenger (2.2.5) lib/phusion_passenger/spawn_manager.rb:154:in `spawn_application'
  passenger (2.2.5) lib/phusion_passenger/spawn_manager.rb:287:in `handle_spawn_application'
  passenger (2.2.5) lib/phusion_passenger/abstract_server.rb:352:in `__send__'
  passenger (2.2.5) lib/phusion_passenger/abstract_server.rb:352:in `main_loop'
  passenger (2.2.5) lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously'

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