How to call a custom sibling method of custom helper in codeigniter and use database

EDIT

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




 function getCrud($table_name, $subject)
{

    $CI =& get_instance();
    $CI->load->database();

    $crud = new grocery_Crud();
    $crud->set_table($table_name);
    $crud->set_subject($subject);
    $crud->unset_read();
    $crud->unset_clone();
    $crud->where(array($table_name.'.flag' => '1'));

    $crud->callback_delete(function ($primary_key) use ($table_name) {
        return $CI->db->update($table_name, array('flag'=>'0'), array('id'=>$primary_key));
    });

    return $crud;
}

 function oneToMany($table_name, $subject, $rel_table,$field='name')
{

    $crud = getGrocreyCrud($table_name, $subject);
    $crud->set_relation($rel_table.'_id', $rel_table, 'name', array('flag' => '1'));
    $output = $crud->render();
    return $output;
}

I can not call the above function getCrud using the ci get instance. Are there any other methods ??

return $CI->db->update($table_name, array('flag'=>'0'), array('id'=>$primary_key)); when using these line of codes in controller ($CI will be $this in controller) I am able to set the flag to 0 but here in helper its not happening

    class Gc_script
    {
        public $CI;
        public function __construct()
        {
            $this->CI =& get_instance();
            $this->CI->config->item('base_url');
        }

        public function getGrocreyCrud($table_name, $read=null)
        {
            $crud = new grocery_Crud();
            $crud->set_table($table_name);
            $crud->set_subject(ucwords(str_replace('_', ' ', $table_name)));

            $crud->callback_delete(function ($primary_key) use ($table_name) {
                return  $this->CI->db->update($table_name, array('flag'=>'0'), array('id'=>$primary_key));
            });

            return $crud;
        }
   }