Cactiverecord Rules To Check If Data Already Exists

Dear all,

I am creating new datasets but currently I don´t know how to check it data already exists in the database. I have read the the save() should automatically check the rules function. Is that true?

I think it is not working because the line

array('id_os', 'exists', 'on'=>'insert_post'),

is not good.

I have

	public function actionCreate()


		$model=new Operatingsystem;

		// Uncomment the following line if AJAX validation is needed

		// $this->performAjaxValidation($model);











and this rules function.

	public function rules()


		// NOTE: you should only define rules for those attributes that

		// will receive user inputs.

		return array(

			array('id_os', 'required'),

			array('id_os', 'length', 'max'=>20),

			array('os_name', 'length', 'max'=>45),

			// The following rule is used by search().

			// Please remove those attributes that should not be searched.

			array('id_os, os_name', 'safe', 'on'=>'search'),

                        array('id_os', 'exists', 'on'=>'insert_post'),




I found the solution. The rule is

array('id_os', 'unique'),

Thanks , it worked