title: rails3, confused about using params[:filename].tempfile.path vs params[:filename][:tempfile].path
body: <p>On a Rails 3 app hosted at Heroku, where a multipart file is POSTed to my app, I'm trying to use some sample code that says :</p>
  
  <pre><code>File.open(params['filename'][:tempfile].path)
  </code></pre>
  
  <p>however, my logs show the error NoMethodErr no such method as tempfile.</p>
  
  <p>I also tried </p>
  
  <pre><code>File.open(params[:filename].tempfile.path)
  </code></pre>
  
  <p>got the same error.</p>
  
  <p>I added  <code>require 'tempfile'</code> to my Controller, made no difference.</p>