title: Doing something before saving a form used with HABTM
body: <p>I currently have 3 tables.</p>
  
  <p>snippet
  tags
  snippet_tags</p>
  
  <p>I'm using HABTM.</p>
  
  <p>So I did a form to save a snippet with tags. Keywords are in a text field, separated by commas.</p>
  
  <p>What I need to do is to take the string from this text field, loop on the keywords, check if they exist, if not create them, and THEN save the snippet.</p>
  
  <p>I tried with a before_save but it doesn't seem to go by that way..</p>
  
  <p>So if you could help me, it'd great!</p>
  
  <p>Thanks a lot!</p>