title: How to call a method when a particular validation fails?
body: <p>I'm checking the uniqueness of email for users as:</p>
  
  <pre><code>validates_uniqueness_of :email
  </code></pre>
  
  <p>That's fine. But, I need to call a method when this particular validation fails.</p>
  
  <p>Thus, How to call a method when a particular validation fails in rails model?!</p>
  
  <p>TIA!</p>