CI框架装载器Loader.php源码分析

顾名思义，装载器就是加载元素的，使用CI时，经常加载的有：

$this->load->library()
$this->load->view()
$this->load->model()
$this->load->database()
$this->load->helper()
$this->load->config()
$this->load->add_package_path()

代码如下:
/**
 * Loader Class
 *
 * 用户加载views和files，常见的函数有model(),view(),library(),helper()
 *
 * Controller的好助手，$this->load =& load_class('Loader', 'core');，加载了loader，Controller就无比强大了
 */
class CI_Loader {
 protected $_ci_ob_level;
 protected $_ci_view_paths  = array();
 protected $_ci_library_paths = array();
 protected $_ci_model_paths  = array();
 protected $_ci_helper_paths  = array();
 protected $_base_classes  = array(); // Set by the controller class
 protected $_ci_cached_vars  = array();
 protected $_ci_classes   = array();
 protected $_ci_loaded_files  = array();
 
 protected $_ci_models   = array();
 protected $_ci_helpers   = array();
 protected $_ci_varmap   = array('unit_test' => 'unit',
           'user_agent' => 'agent');
 public function __construct()
 {      
                //获取缓冲嵌套级别
  $this->_ci_ob_level  = ob_get_level();
  //library路径
                $this->_ci_library_paths = array(APPPATH, BASEPATH);
                //helper路径
  $this->_ci_helper_paths = array(APPPATH, BASEPATH);
                //model路径
  $this->_ci_model_paths = array(APPPATH);
                //view路径
  $this->_ci_view_paths = array(APPPATH.'views/' => TRUE);
  log_message('debug', "Loader Class Initialized");
 }
 // --------------------------------------------------------------------
 /**
  * 初始化Loader
  *
  */
 public function initialize()
 {
  $this->_ci_classes = array();
  $this->_ci_loaded_files = array();
  $this->_ci_models = array();
                //将is_loaded（common中记录加载核心类函数）加载的核心类交给_base_classes