CI框架扩展系统核心类的方法分析

$config['subclass_prefix'] = 'MY_';

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
abstract class Admin_Controller extends CI_Controller
{
  /**
  * _admin
  * 保存当前登录用户的信息
  *
  * @var object
  * @access public
  **/
  public $_admin = NULL;
  /**
  * 构造函数
  *
  * @access public
  * @return void
  */
  public function __construct()
  {
    parent::__construct();
    $this->load->library('session');
    $this->settings->load('backend');
    $this->load->switch_theme(setting('backend_theme'));
    $this->_check_login();
    $this->load->library('acl');
    $this->load->library('plugin_manager');
  }
 /**
  * 检查用户是否登录
  *
  * @access protected
  * @return void
  */
  protected function _check_login()
  {
    if ( ! $this->session->userdata('uid'))
    { 
      redirect(setting('backend_access_point') . '/login');
    }
    else
    {
      $this->_admin = $this->user_mdl->get_full_user_by_username($this->session->userdata('uid'), 'uid');
      if ($this->_admin->status != 1)
      {
        $this->session->set_flashdata('error', "此帐号已被冻结,请联系管理员!");
        redirect(setting('backend_access_point') . '/login');
      }
    }
  }
 /**
  * 加载视图
  *
  * @access protected
  * @param string
  * @param array
  * @return void
  */
  protected function _template($template, $data = array())
  {
    $data['tpl'] = $template;
    $this->load->view('sys_entry', $data);
  }
 /**
  * 检查权限
  *
  * @access protected
  * @param string
  * @return void
  */
  protected function _check_permit($action = '', $folder = '')
  {
    if ( ! $this->acl->permit($action, $folder))
    {
      $this->_message('对不起，你没有访问这里的权限！', '', FALSE);
    }
  }
 /**
  * 信息提示
  *
  * @access public
  * @param string
  * @param string
  * @param bool
  * @param string
  * @return void
  */
  public function _message($msg, $goto = '', $auto = TRUE, $fix = '')
  {
    if($goto == '')
    {
      $goto = isset($_SERVER['HTTP_REFERER']) ? $_SERVER['HTTP_REFERER'] : site_url();
    }
    else
    {
      $goto = strpos($goto, 'http') !== false ? $goto : backend_url($goto);  
    }
    $goto .= $fix;
    $this->_template('sys_message', array('msg' => $msg, 'goto' => $goto, 'auto' => $auto));
    echo $this->output->get_output();
    exit();
  }
}

abstract class Font_Controller extends CI_Controller{
 public function __construct() {
  parent::__construct();
 }
 //前台加载视图方法
 public function _template($template, $data = array()){
  $data['nav'] = $this->get_nav();
  $data['tpl'] = $template;
  $this->load->view('default',$data);
 }
 //公共导航信息
 public function get_nav(){
 }
 //公共友情链接信息
 public function get_friendlink(){
 }
}