title: Ruby on rails, Change column value on update of other column value
body: <p>I have two columns related to each other in a Rails model:</p>
  
  <pre><code>Article.body
  Article.body_updated_on
  </code></pre>
  
  <p>I want to change the <code>Article.body_updated_on</code> to <code>Time.now</code>, every time <code>Article.body</code> is updated. If any other fields updated nothing needs to be happen.</p>