How joomla recognition, which user is login, in com_content? - Joomla! Forum - community, help and support

i'm sorry if it's amateur question in joomla developing it's important me.
in com_content need username login front-end.
my query

code: select all

select username #__users id='$id'


the problem where id='$id' part, pleas pay attention in com_content can't use getvar. example:

code: select all

$id = jrequest::getvar("id");


so in query $id null.
please tell me, by query can logged in users, username ?

the user's id not part of jrequest, if user logged in, can user object:

code: select all

$user = jfactory::getuser();
$id = 0;
$username = '';
// not guest?
if ($user->get('guest') != 1) {
    $userid      = (int) $user->get('id');
    $username = $user->get('username');
} 

- or just:

code: select all

$user        = jfactory::getuser();
$userid      = (int) $user->get('id');
$username = $user->get('username');