Session Handling From Models

[eluser]Thimuth[/eluser]
Can we set session variables from the model classes?
When i call " $this->session->set_userdata($userdata); " with inside a model class, it gives an error.
Does the session formation is a controller specific task?

[eluser]flaky[/eluser]
example

Code:

$CI =& get_instance();
$CI->session->userdata('user_id);