public function index($id = null, $slug = ''){
// Fetch the article
        //$this->db->where('pubdate <=', date('Y-m-d'));
        $this->data['article'] = $this->mberita->get_by_id($id,$slug);
       // Return 404 if not found
        count($this->data['article']) || show_404(uri_string());

        // Redirect if slug was incorrect
        $requested_slug = $this->uri->segment(3);
        $set_slug = $this->data['article']->slug;
        if ($requested_slug != $set_slug) {
            redirect('article/' . $this->data['article']->id . '/' . url_title($set_slug), 'location', '301');


        // Load view
        $this->data['contents'] = 'article';
        $this->load->view('template/wrapper/mahasiswa/wrapper_article', $this->data);

    }

<div class="post-buttons">
       <a href="<?php echo 'article/' . intval($dt->id) . '/' . url_title($dt->slug) ; ?>" class="ui black label">
             Read More
       </a>
 </div>

tkd/index.php/article/77/kejurnas-mahasiswa

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?/$1 [L]

$route['article/(:num)/(:any)'] = "article/show_article/$1/$2"; //where article is controller and show_article is "behind the scene" method that takes over your index(); not a single user will know about it

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Article extends CI_Controller {
//I can spot that you are extending your controller NOT by CI_Controller because of usage $this->data[]

    public function __construct() {
        //constructor
        parent::__construct();
        $this->load->model('article_model', 'article'); //load model article_model and create alias "article"

    }

    public function index() {
        //let this be empty or redirect if no ID is sent to the controller
        redirect(); //redirect to default_controller
    }

    public function show_article($id = FALSE, $slug = FALSE) {
        if ($id === FALSE) redirect(); // no id? redirect to default_controller
        if ($slug === FALSE) {
            //slug is not sent to the article
            //you should do nothing if this happens but you may require reload page with correct slug
                //get slug by id
                //redirect(/article/$id/slug_by_id)
        }

        // Fetch the article
        //$this->db->where('pubdate <=', date('Y-m-d'));
        if ($this->data['article'] = $this->article->get($id)) {
            //all good we can show result
            $this->data['contents'] = 'article';
            $this->load->view('template/wrapper/mahasiswa/wrapper_article', $this->data);

        } else {
            //get() method returns FALSE
            redirect(); //id is not valid or there is no such record with id = $id
        }

    }

}

/* End of file article.php */
/* Location: ./application/controllers/article.php */

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Article extends CI_Model {

    public function __construct() {
        parent::__construct();
        //Do your magic here
    }

    public function get( $id = FALSE ) {
        if ($id === FALSE) return FALSE;

        $q = $this->db->get_where('article', array('id' => $id)); // table = 'article'

        return ($q->num_rows() > 0) ? $q->result() : FALSE;

    }


}

/* End of file article_model.php */
/* Location: ./application/models/article_model.php */