Checking for duplicate records

If you want to validate a form field (such as a user ID field) and make sure that the selected user ID does not already exist in the database, here’s a simple way to do it:

class UserController extends AppController
{
   function add()
   {
      if ($this->User->isUnique($this->data['User']['username'])) 
      { 
         if ($this->User->save($this->data))
         {
            $this->flash('User has been saved.','/users/index');
         }
      }
   }
}

class User extends AppModel
{
   function isUnique($userName)
   {
      $userNames['User.username'] = $userName;
 
      if ($this->hasAny($userNames))
      {
         $this->invalidate('userNameExists'); 
 
         return false;
      }
      else 
      {
         return true;
      }
   }
}

echo $html->tagErrorMsg('User/userNameExists', 'User name already exists.  Please choose another.')