CodeIgniter Ion Auth - set_hooks example

gistfile1.aw

//this would probably be in a library or model
class activity
{
    function add($type)
    {
        $this->db->insert('activity', array(
            'type'     => $type,
            'datetime' => 'now()',
        ));
    }
}

//set the hook
$this->ion_auth->set_hook('post_register', 'add_meta', 'activity', 'add', array('user_added'));

//other stuff...

//after this is called the hook will be executed automatically
$this->ion_auth->register(...

Hello,@benedmunds
I can run your example. The data in the table is entered correctly.by:
$this->ion_auth->set_hook('post_register', 'add_meta', 'activity', 'add', array('user_added'));
But why does not the following command answer?
$this->ion_auth->set_hook('post_activate', 'add_meta', 'activity', 'add', array('user_added'));
And i reviewed the following. The correct operation is not done.

$this->ion_auth->set_hook(array('post_activate', 'post_activate_successful'), 'add_meta',  'activity', 'add', array('user_added'));
$this->ion_auth->set_hook('post_activate_successful', 'add_meta',  'activity', 'add', array('user_added'));

please guide me?