Problem with Getting data from Model

[eluser]Tanvir[/eluser]
Hello, I m new to CI, I cant get data from model class. Here is my classes-

Code:

<?php
class Blog_Model extends CI_Model
{
function __construct()
{parent::__construct();}

function showTable(){
$query=$this->$db->get('user');   // line- 17
foreach ($query->result() as $row)
{
    echo $row->name;
}

}

This is my controller class -

Code:

<?php

class Blog extends CI_Controller
{
    public function __construct()
    {parent :: __construct() ;    }
    public function index()
    {
        $this->load->model('Blog_Model','dbmodel');
        $this->dbmodel->showTable();    
    }
        
}
?>

this is the error -
A PHP Error was encountered

Severity: Notice
Message: Undefined variable: db
Filename: models/blog_model.php
Line Number: 17
Fatal error: Cannot access empty property in C:\xampp\htdocs\CodeIgniter\system\core\Model.php on line 50