<"white-space:pre">		</span>//加载Loader对象，再利用Loader对象对程序内一系列资源进行加载<span style="white-space:pre">	</span>
		$this->load =& load_class('Loader', 'core');

		$this->load->initialize();
		
		log_message('debug', "Controller Class Initialized");
	}

	//这个函数对外提供了控制器的单一实例
	public static function &get_instance()
	{
		return self::$instance;
	}
}


//*BASEPATH/system/core/CodeIgniter.php
	// Load the base controller class
	require BASEPATH.'core/Controller.php';

	//通过这个全局函数就得到了控制器的实例，得到了这个超级对象，
	//意味着在程序其他地方调用这个函数，就能得到整个框架的控制权
	function &get_instance()
	{
		return CI_Controller::get_instance();
	}

	// 加载对应的控制器类
	// 注意：Router类会自动使用 router->_validate_request() 验证控制器路径
	if ( ! file_exists(APPPATH.'controllers/'.$RTR->fetch_directory().$RTR->fetch_class().'.php'))
	{
		show_error('Unable to load your default controller. Please make sure the controller specified in your Routes.php file is valid.');
	}

	include(APPPATH.'controllers/'.$RTR->fetch_directory().$RTR->fetch_class().'.php');

	$class = $RTR->fetch_class(); //Controller class name
	$method = $RTR->fetch_method(); //action name

	//.....

	// 调用请求的函数
	// uri中除了class/function之外的段也会被传递给调用的函数
	call_user_func_array(array(&$CI, $method), array_slice($URI->rsegments, 2));

	//输出最终的内容到浏览器
	if ($EXT->_call_hook('display_override') === FALSE)
	{
		$OUT->_display();
	}
	

//*BASEPATH/system/core/Loader.php
	//看一个Loader类加载model的例子。这里只列出了部分代码
	public function model($model, $name = '', $db_conn = FALSE)
	{
		$CI =& get_instance();
		if (isset($CI->$name))
		{
			show_error('The model name you are loading is the name of a resource that is already being used: '.$name);
		}

		$model = strtolower($model);

		//依次根据model类的path进行匹配，如果找到了就加载
		foreach ($this->_ci_model_paths as $mod_path)
		{
			if ( ! file_exists($mod_path.'models/'.$path.$model.'.php'))
			{
				continue;
			}

			if ($db_conn !== FALSE AND ! class_exists('CI_DB'))
			{
				if ($db_conn === TRUE)
				{
					$db_conn = '';
				}

				$CI->load->database($db_conn, FALSE, TRUE);
			}

			if ( ! class_exists('CI_Model'))
			{
				load_class('Model', 'core');
			}

			require_once($mod_path.'models/'.$path.$model.'.php');

			$model = ucfirst($model);

			//这里依然将model对象注册成控制器类的成员变量。Loader在加载其他资源的时候也会这么做
			$CI->$name = new $model();

			$this->_ci_models[] = $name;
			return;
		}

		// couldn't find the model
		show_error('Unable to locate the model you have specified: '.$model);
	}

//*BASEPATH/system/core/Model.php
	//__get()是一个魔术方法，当读取一个未定义的变量的值时就会被调用
	//如下是Model基类对__get()函数的一个实现，使得在Model类内，可以像直接在控制器类内一样(例如$this->var的方式)去读取它的变量
	function __get($key)
	{
		$CI =& get_instance();
		return $CI->$key;
	}