如何在Ubuntu上安装g ++ - 4.7？(How to install g++-4.7 on Ubuntu?)

 这是因为根据您尝试上传的CSV文件的大小，文件类型可能是StringIO或TempFile对象。 所以你可能会采取适当的行动，具体取决于它是什么。 请参阅此答案以获得解释。 接下来，您的代码变为： 
 
file_data = params[:file]
if file.respond_to?(:read)
  csv_text = file.read
elsif file.respond_to?(:path)
  csv_text = File.read(file.path)
else
  logger.error "Bad file_data: #{file.class.name}: #{file.inspect}"
end
@rowarraydisp = CSV.parse(csv_text, :headers => true)
 
 另外，您在form_tag指定了GET方法，在上传表单的情况下，您要发布数据，因此我只是完全删除该方法或正确指定方法作为post。 

That's because depending on the size of the CSV file you're trying to upload, the type of file might either be a StringIO or TempFile object. So you may wan to take appropriate action, depending on which it is. See this answer for an explanation. Following that your code becomes something like:
 
file_data = params[:file]
if file.respond_to?(:read)
  csv_text = file.read
elsif file.respond_to?(:path)
  csv_text = File.read(file.path)
else
  logger.error "Bad file_data: #{file.class.name}: #{file.inspect}"
end
@rowarraydisp = CSV.parse(csv_text, :headers => true)
 
Also, you have specified method as GET in form_tag, in your case when uploading a form, you are posting data, so I'd just remove the method altogether or correctly specify the method as post.