$user = User::get(1);
echo $user->append(['status_text'])->toJson();

$user = User::find(1);
echo $user->appendRelationAttr('profile',['email','nickname'])->toJson();


我想问，
$value = Nav::all();
echo json($value);
exit();
我怎么得到nav_url
public function getNavUrlAttr($value,$data){

}