Yii ActiveRecord Unique validator example

Example.php

<?php


class Example extends CActiveRecord
{
	// ...

	public function rules()
	{
		return array(
			array(
				'username', 'unique', 'on'=>'register',
				'allowEmpty' => false,
				'attributeName' => 'username',
				'caseSensitive'=> false,
				'className'=>'Example',
				'message'=>'Sorry, this username has already been taken.',
			),
		);
	}

	// ...
}