Ruby on rails 联合0.5.5/mongo映射器0.8.6-命名错误（未定义的方法“etag'；用于网格…）

我们使用

• 轨道2.3.8
• Ruby 1.9.2
• Mongo mapper 0.8.6
• 接头0.5.5
• 魔杖0.4

在以下代码行中使用etag时，我们会遇到此错误：

return  if fresh_when( :etag => @lesson.video.etag, :last_modified => @lesson.updated_at.utc )

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任何帮助都将不胜感激

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-Mei

Mei，请使用hash[]方法获取etag属性：

@lesson.video['etag']

Processing LessonsController#video to mp4 (for 127.0.0.1 at 2011-12-22 20:32:51) [GET]
Parameters: {"subdomains"=>["www"], "controller"=>"lessons", "action"=>"video",  "id"=>"4ccf79526905582045000041", "format"=>"mp4"}

NoMethodError (undefined method `etag' for #<GridIO _id: 4ccf846a1204cc1b2f0000e9>):  
joint (0.5.5) lib/joint/attachment_proxy.rb:32:in `method_missing'
app/controllers/lessons_controller.rb:71:in `video'

class Lesson
  include MongoMapper::Document
  plugin Joint

  (other stuff...)

  attachment :image                                                            
  attachment :video                                                            

  timestamps!                                                                  
end