How to use messages component

I tried to write this code but nothing happens. I expected an error of Yii. I expected a mistake because I did not create that class.

    'components' => array(

        'messages' => array(

            'onBeginRequest' => array (

                'MyClassOnBeginRequest' => 'methodOnBeginRequest'



onBeginRequest is rised from CApplication -

CMessageSource (‘messages’) is a child of CApplicationComponent so it does not rise this event

I see. CMessageSource rise only onMissingTranslation event. =( I am only at page 13 of Application Development Cookbook =). I am just trying.