title: Rails STI using ONE form
body: <p>I have a form that allows me to add files of different formats to a stream. So, a stream is made up of many files, these files are XML files but basically have different schemas. I have one form that allows the user to add whatever file they want, I am using STI (which works great when data is already in the table), my trouble is adding the data to the table.</p>
  
  <p>The form has 1 input field, just a file_field that allows the user to select the file they want to upload. Since I only have one form I'm not able to instantiate the correct object, I have to do it programatically.. and I'm not sure how to do it.</p>
  
  <p>Do I just (or can I) add a drop down with the possible types, and call that field 'type' so that when the form is submitted rails will instantiate the write type of object because the type attribute is provided?</p>
  
  <p>What is the best practice for this.. I'm running rails 2.3.4.</p>