URI Class CodeIgniter 1.7.2

[eluser]codeworxx[/eluser]
Dear again Guys,

i have a problem with the CodeIgniter URI Class.

In the UserGuide theres a notice, that the Class is automaticall initalized by the System, but when i create a

Code:

application/controller/listings.php

with

Code:

class Listings extends Controller
{
    function listings()
    {
        echo $this->uri->segement(2);
    }
}

I get an Error, "Undefined property: Listings::$uri" ????

I want to open the URL: index.php/listings/computer

Whats wrong?

Thanks,
Sascha

[eluser]codeworxx[/eluser]
Okay, Problem solved by myself. Thank you!