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
  $this->_base_classes =& is_loaded();
  //加载autoload.PHP配置中文件
  $this->_ci_autoloader();
  return $this;
  }
  // --------------------------------------------------------------------
  /**

• 检测类是否加载
  */
  public function is_loaded($class)
  {
  if (isset($this->_ci_classes[$class]))
  {
  return $this->_ci_classes[$class];
  }
  return FALSE;
  }
  // --------------------------------------------------------------------
  /**
• 加载Class
  */
  public function library($library = '',$params = NULL,$object_name = NULL)
  {
  if (is_array($library))
  {
  foreach ($library as $class)
  {
  $this->library($class,$params);
  }
  return;
  }
  //如果$library为空或者已经加载。。。
  if ($library == '' OR isset($this->_base_classes[$library]))
  {
  return FALSE;
  }
  if ( ! is_null($params) && ! is_array($params))
  {
  $params = NULL;
  }
  $this->_ci_load_class($library,$params,$object_name);
  }
  // --------------------------------------------------------------------
  /**
• 加载和实例化model
  */
  public function model($model,$name = '',$db_conn = FALSE)
  {
  //CI支持数组加载多个model
  if (is_array($model))
  {
  foreach ($model as $babe)
  {
  $this->model($babe);
  }
  return;
  }
  if ($model == '')
  {
  return;
  }
  $path = '';
  // 是否存在子目录
  if (($last_slash = strrpos($model,'/')) !== FALSE)
  {
  // The path is in front of the last slash
  $path = substr($model,$last_slash + 1);
  // And the model name behind it
  $model = substr($model,$last_slash + 1);
  }
  if ($name == '')
  {
  $name = $model;
  }
  if (in_array($name,$this->_ci_models,TRUE))
  {
  return;
  }
  $CI =& get_instance();
  if (isset($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); //model文件名全小写
  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);
  $CI->$name = new $model();
  //保存在Loader::_ci_models中，以后可以用它来判断某个model是否已经加载过。
  $this->_ci_models[] = $name;
  return;
  }
  // couldn't find the model
  show_error('Unable to locate the model you have specified: '.$model);
  }
  // --------------------------------------------------------------------
  /**
• 数据库Loader
  */
  public function database($params = '',$return = FALSE,$active_record = NULL)
  {
  // Grab the super object
  $CI =& get_instance();
  // 是否需要加载db
  if (class_exists('CI_DB') AND $return == FALSE AND $active_record == NULL AND isset($CI->db) AND is_object($CI->db))
  {
  return FALSE;
  }
  require_once(BASEPATH.'database/DB.PHP');
  if ($return === TRUE)
  {
  return DB($params,$active_record);
  }
  // Initialize the db variable. Needed to prevent
  // reference errors with some configurations
  $CI->db = '';
  // Load the DB class
  $CI->db =& DB($params,$active_record);
  }
  // --------------------------------------------------------------------
  /**
• 加载数据库工具类
  */
  public function dbutil()
  {
  if ( ! class_exists('CI_DB'))
  {
  $this->database();
  }
  $CI =& get_instance();
  // for backwards compatibility,load dbforge so we can extend dbutils off it
  // this use is deprecated and h3ly discouraged
  $CI->load->dbforge();
  require_once(BASEPATH.'database/DB_utility.PHP');
  require_once(BASEPATH.'database/drivers/'.$CI->db->dbdriver.'/'.$CI->db->dbdriver.'_utility.PHP');
  $class = 'CIDB'.$CI->db->dbdriver.'_utility';
  $CI->dbutil = new $class();
  }
  // --------------------------------------------------------------------
  /**
• Load the Database Forge Class
• @returnstring
  */
  public function dbforge()
  {
  if ( ! class_exists('CI_DB'))
  {
  $this->database();
  }
  $CI =& get_instance();
  require_once(BASEPATH.'database/DB_forge.PHP');
  require_once(BASEPATH.'database/drivers/'.$CI->db->dbdriver.'/'.$CI->db->dbdriver.'_forge.PHP');
  $class = 'CIDB'.$CI->db->dbdriver.'_forge';
  $CI->dbforge = new $class();
  }
  // --------------------------------------------------------------------
  /**
• 加载视图文件
  */
  public function view($view,$vars = array(),$return = FALSE)
  {
  return $this->_ci_load(array('_ci_view' => $view,'_ci_vars' => $this->_ci_object_to_array($vars),'_ci_return' => $return));
  }
  // --------------------------------------------------------------------
  /**
• 加载普通文件
  */
  public function file($path,$return = FALSE)
  {
  return $this->_ci_load(array('_ci_path' => $path,'_ci_return' => $return));
  }
  // --------------------------------------------------------------------
  /**
• 设置变量
• Once variables are set they become available within
• the controller class and its "view" files.

• */
  public function vars($vars = array(),$val = '')
  {
  if ($val != '' AND is_string($vars))
  {
  $vars = array($vars => $val);
  }
  $vars = $this->_ci_object_to_array($vars);
  if (is_array($vars) AND count($vars) > 0)
  {
  foreach ($vars as $key => $val)
  {
  $this->_ci_cached_vars[$key] = $val;
  }
  }
  }
  // --------------------------------------------------------------------
  /**

• 检查并获取变量
  */
  public function get_var($key)
  {
  return isset($this->_ci_cached_vars[$key]) ? $this->_ci_cached_vars[$key] : NULL;
  }
  // --------------------------------------------------------------------
  /**
• 加载helper
  */
  public function helper($helpers = array())
  {
  foreach ($this->_ci_prep_filename($helpers,'_helper') as $helper)
  {
  if (isset($this->_ci_helpers[$helper]))
  {
  continue;
  }
  $ext_helper = APPPATH.'helpers/'.config_item('subclass_prefix').$helper.'.PHP';
  // 如果是扩展helper的话
  if (file_exists($ext_helper))
  {
  $base_helper = BASEPATH.'helpers/'.$helper.'.PHP';
  if ( ! file_exists($base_helper))
  {
  show_error('Unable to load the requested file: helpers/'.$helper.'.PHP');
  }
  include_once($ext_helper);
  include_once($base_helper);
  $this->_ci_helpers[$helper] = TRUE;
  log_message('debug','Helper loaded: '.$helper);
  continue;
  }
  // 如果不是扩展helper，helper路径中加载helper
  foreach ($this->_ci_helper_paths as $path)
  {
  if (file_exists($path.'helpers/'.$helper.'.PHP'))
  {
  include_once($path.'helpers/'.$helper.'.PHP');
  $this->_ci_helpers[$helper] = TRUE;
  log_message('debug','Helper loaded: '.$helper);
  break;
  }
  }
  // 如果该helper还没加载成功的话，说明加载helper失败
  if ( ! isset($this->_ci_helpers[$helper]))
  {
  show_error('Unable to load the requested file: helpers/'.$helper.'.PHP');
  }
  }
  }
  // --------------------------------------------------------------------
  /**
• 可以看到helpers调用也是上面的helper,只是helpers的别名而已
  */
  public function helpers($helpers = array())
  {
  $this->helper($helpers);
  }
  // --------------------------------------------------------------------
  /**
• 加载language文件
  */
  public function language($file = array(),$lang = '')
  {
  $CI =& get_instance();
  if ( ! is_array($file))
  {
  $file = array($file);
  }
  foreach ($file as $langfile)
  {
  $CI->lang->load($langfile,$lang);
  }
  }
  // --------------------------------------------------------------------
  /**
• 加载配置文件
  */
  public function config($file = '',$use_sections = FALSE,$fail_gracefully = FALSE)
  {
  $CI =& get_instance();
  $CI->config->load($file,$use_sections,$fail_gracefully);
  }
  // --------------------------------------------------------------------
  /**
• Driver
• 加载 driver library
  /
  public function driver($library = '',$object_name = NULL)
  {
  if ( ! class_exists('CI_Driver_Library'))
  {
  // we aren't instantiating an object here,that'll be done by the Library itself
  require BASEPATH.'libraries/Driver.PHP';
  }
  if ($library == '')
  {
  return FALSE;
  }
  // We can save the loader some time since Drivers will always* be in a subfolder,
  // and typically identically named to the library
  if ( ! strpos($library,'/'))
  {
  $library = ucfirst($library).'/'.$library;
  }
  return $this->library($library,$object_name);
  }
  // --------------------------------------------------------------------
  /**
• 添加 Package 路径
• 把package路径添加到库，模型，助手，配置路径
  */
  public function add_package_path($path,$view_cascade=TRUE)
  {
  $path = rtrim($path,'/').'/';
  array_unshift($this->_ci_library_paths,$path);
  array_unshift($this->_ci_model_paths,$path);
  array_unshift($this->_ci_helper_paths,$path);
  $this->_ci_view_paths = array($path.'views/' => $view_cascade) + $this->_ci_view_paths;
  $config =& $this->_ci_get_component('config');
  array_unshift($config->_config_paths,$path);
  }
  // --------------------------------------------------------------------
  /**
• 获取Package Paths，默认不包含BASEPATH
  */
  public function get_package_paths($include_base = FALSE)
  {
  return $include_base === TRUE ? $this->_ci_library_paths : $this->_ci_model_paths;
  }
  // --------------------------------------------------------------------
  /**
• 剔除Package Path
• Remove a path from the library,model,and helper path arrays if it exists
• If no path is provided,the most recently added path is removed.

• */
  public function remove_package_path($path = '',$remove_config_path = TRUE)
  {
  $config =& $this->_ci_get_component('config');
  if ($path == '')
  {
  $void = array_shift($this->_ci_library_paths);
  $void = array_shift($this->_ci_model_paths);
  $void = array_shift($this->_ci_helper_paths);
  $void = array_shift($this->_ci_view_paths);
  $void = array_shift($config->_config_paths);
  }
  else
  {
  $path = rtrim($path,'/').'/';
  foreach (array('_ci_library_paths','_ci_model_paths','_ci_helper_paths') as $var)
  {
  if (($key = array_search($path,$this->{$var})) !== FALSE)
  {
  unset($this->{$var}[$key]);
  }
  }
  if (isset($this->_ci_view_paths[$path.'views/']))
  {
  unset($this->_ci_view_paths[$path.'views/']);
  }
  if (($key = array_search($path,$config->_config_paths)) !== FALSE)
  {
  unset($config->_config_paths[$key]);
  }
  }
  // 保证应用默认的路径依然存在
  $this->_ci_library_paths = array_unique(array_merge($this->_ci_library_paths,array(APPPATH,BASEPATH)));
  $this->_ci_helper_paths = array_unique(array_merge($this->_ci_helper_paths,BASEPATH)));
  $this->_ci_model_paths = array_unique(array_merge($this->_ci_model_paths,array(APPPATH)));
  $this->_ci_view_paths = array_merge($this->_ci_view_paths,array(APPPATH.'views/' => TRUE));
  $config->_config_paths = array_unique(array_merge($config->_config_paths,array(APPPATH)));
  }
  // --------------------------------------------------------------------
  /**

• Loader
• This function is used to load views and files.
• Variables are prefixed with ci to avoid symbol collision with
• variables made available to view files
• @paramarray
• @returnvoid
  /
  protected function _ci_load($_ci_data)
  {
  // Set the default data variables
  foreach (array('_ci_view','_ci_vars','_ci_path','_ci_return') as $_ci_val)
  {
  $$_ci_val = ( ! isset($_ci_data[$_ci_val])) ? FALSE : $_ci_data[$_ci_val];
  }
  $file_exists = FALSE;
  //如果$_ci_path不为空，则说明当前要加载普通文件。Loader::file才会有path
  if ($_ci_path != '')
  {
  $_ci_x = explode('/',$_ci_path);
  $_ci_file = end($_ci_x);
  }
  else
  {
  $_ci_ext = pathinfo($_ci_view,PATHINFO_EXTENSION);
  $_ci_file = ($_ci_ext == '') ? $_ci_view.'.PHP' : $_ci_view;
  foreach ($this->_ci_view_paths as $view_file => $cascade)
  {
  if (file_exists($view_file.$_ci_file))
  {
  $_ci_path = $view_file.$_ci_file;
  $file_exists = TRUE;
  break;
  }
  if ( ! $cascade)
  {
  break;
  }
  }
  }
  //view文件不存在则会报错
  if ( ! $file_exists && ! file_exists($_ci_path))
  {
  show_error('Unable to load the requested file: '.$_ci_file);
  }
  // 把CI的所有属性都传递给loader，view中$this指的是loader
  $_ci_CI =& get_instance();
  foreach (get_object_vars($_ci_CI) as $_ci_key => $_ci_var)
  {
  if ( ! isset($this->$_ci_key))
  {
  $this->$_ci_key =& $_ci_CI->$_ci_key;
  }
  }
  /
• Extract and cache variables
• You can either set variables using the dedicated $this->load_vars()
• function or via the second parameter of this function. We'll merge
• the two types and cache them so that views that are embedded within
• other views can have access to these variables.
  /
  if (is_array($_ci_vars))
  {
  $this->_ci_cached_vars = array_merge($this->_ci_cached_vars,$_ci_vars);
  }
  extract($this->_ci_cached_vars);
  /
• 将视图内容放到缓存区

• /
  ob_start();
  // 支持短标签
  if ((bool) @ini_get('short_open_tag') === FALSE AND config_item('rewrite_short_tags') == TRUE)
  {
  echo eval('?>'.preg_replace("/;\s*\?>/","; ?>",str_replace('<?=','<?php echo ',file_get_contents($_ci_path))));
  }
  else
  {
  include($_ci_path); // include() vs include_once() allows for multiple views with the same name
  }
  log_message('debug','File loaded: '.$_ci_path);
  // 是否直接返回view数据
  if ($_ci_return === TRUE)
  {
  $buffer = ob_get_contents();
  @ob_end_clean();
  return $buffer;
  }
  //当前这个视图文件是被另一个视图文件通过$this->view()方法引入，即视图文件嵌入视图文件
  if (ob_get_level() > $this->_ci_ob_level + 1)
  {
  ob_end_flush();
  }
  else
  { ////把缓冲区的内容交给Output组件并清空关闭缓冲区。
  $_ci_CI->output->append_output(ob_get_contents());
  @ob_end_clean();
  }
  }
  // --------------------------------------------------------------------
  /**

• 加载类
  */
  protected function _ci_load_class($class,$object_name = NULL)
  {
  // 去掉.PHP和两端的/获取的$class就是类名或目录名+类名
  $class = str_replace('.PHP','',trim($class,'/'));
  // CI允许dir/filename方式
  $subdir = '';
  if (($last_slash = strrpos($class,'/')) !== FALSE)
  {
  // 目录
  $subdir = substr($class,$last_slash + 1);
  // 文件名
  $class = substr($class,$last_slash + 1);
  }
  // 允许加载的类名首字母大写或全小写
  foreach (array(ucfirst($class),strtolower($class)) as $class)
  {
  $subclass = APPPATH.'libraries/'.$subdir.config_item('subclass_prefix').$class.'.PHP';
  // 是否是扩展类
  if (file_exists($subclass))
  {
  $baseclass = BASEPATH.'libraries/'.ucfirst($class).'.PHP';
  if ( ! file_exists($baseclass))
  {
  log_message('error',"Unable to load the requested class: ".$class);
  show_error("Unable to load the requested class: ".$class);
  }
  // Safety: Was the class already loaded by a prevIoUs call?
  if (in_array($subclass,$this->_ci_loaded_files))
  {
  // Before we deem this to be a duplicate request,let's see
  // if a custom object name is being supplied. If so,we'll
  // return a new instance of the object
  if ( ! is_null($object_name))
  {
  $CI =& get_instance();
  if ( ! isset($CI->$object_name))
  {
  return $this->_ci_init_class($class,config_item('subclass_prefix'),$object_name);
  }
  }
  $is_duplicate = TRUE;
  log_message('debug',$class." class already loaded. Second attempt ignored.");
  return;
  }
  include_once($baseclass);
  include_once($subclass);
  $this->_ci_loaded_files[] = $subclass;
  //实例化类
  return $this->_ci_init_class($class,$object_name);
  }
  // 如果不是扩展，和上面类似
  $is_duplicate = FALSE;
  foreach ($this->_ci_library_paths as $path)
  {
  $filepath = $path.'libraries/'.$subdir.$class.'.PHP';
  // Does the file exist? No? Bummer...
  if ( ! file_exists($filepath))
  {
  continue;
  }
  // Safety: Was the class already loaded by a prevIoUs call?
  if (in_array($filepath,$class." class already loaded. Second attempt ignored.");
  return;
  }
  include_once($filepath);
  $this->_ci_loaded_files[] = $filepath;
  return $this->_ci_init_class($class,$object_name);
  }
  } // END FOREACH
  // 如果还没有找到该class，最后的尝试是该class会不会在同名的子目录下
  if ($subdir == '')
  {
  $path = strtolower($class).'/'.$class;
  return $this->_ci_load_class($path,$params);
  }
  // 加载失败，报错
  if ($is_duplicate == FALSE)
  {
  log_message('error',"Unable to load the requested class: ".$class);
  show_error("Unable to load the requested class: ".$class);
  }
  }
  // --------------------------------------------------------------------
  /**
• 实例化已经加载的类
  */
  protected function _ci_init_class($class,$prefix = '',$config = FALSE,$object_name = NULL)
  {
  // 是否有类的配置信息
  if ($config === NULL)
  {
  // Fetch the config paths containing any package paths
  $config_component = $this->_ci_get_component('config');
  if (is_array($config_component->_config_paths))
  {
  // Break on the first found file,thus package files
  // are not overridden by default paths
  foreach ($config_component->_config_paths as $path)
  {
  // We test for both uppercase and lowercase,for servers that
  // are case-sensitive with regard to file names. Check for environment
  // first,global next
  if (defined('ENVIRONMENT') AND file_exists($path .'config/'.ENVIRONMENT.'/'.strtolower($class).'.PHP'))
  {
  include($path .'config/'.ENVIRONMENT.'/'.strtolower($class).'.PHP');
  break;
  }
  elseif (defined('ENVIRONMENT') AND file_exists($path .'config/'.ENVIRONMENT.'/'.ucfirst(strtolower($class)).'.PHP'))
  {
  include($path .'config/'.ENVIRONMENT.'/'.ucfirst(strtolower($class)).'.PHP');
  break;
  }
  elseif (file_exists($path .'config/'.strtolower($class).'.PHP'))
  {
  include($path .'config/'.strtolower($class).'.PHP');
  break;
  }
  elseif (file_exists($path .'config/'.ucfirst(strtolower($class)).'.PHP'))
  {
  include($path .'config/'.ucfirst(strtolower($class)).'.PHP');
  break;
  }
  }
  }
  }
  if ($prefix == '')
  { //system下library
  if (classexists('CI'.$class))
  {
  $name = 'CI_'.$class;
  }
  elseif (class_exists(config_item('subclass_prefix').$class))
  { //扩展library
  $name = config_item('subclass_prefix').$class;
  }
  else
  {
  $name = $class;
  }
  }
  else
  {
  $name = $prefix.$class;
  }
  // Is the class name valid?
  if ( ! class_exists($name))
  {
  log_message('error',"Non-existent class: ".$name);
  show_error("Non-existent class: ".$class);
  }
  // Set the variable name we will assign the class to
  // Was a custom class name supplied? If so we'll use it
  $class = strtolower($class);
  if (is_null($object_name))
  {
  $classvar = ( ! isset($this->_ci_varmap[$class])) ? $class : $this->_ci_varmap[$class];
  }
  else
  {
  $classvar = $object_name;
  }
  // Save the class name and object name
  $this->_ci_classes[$class] = $classvar;
  // 将初始化的类的实例给CI超级句柄
  $CI =& get_instance();
  if ($config !== NULL)
  {
  $CI->$classvar = new $name($config);
  }
  else
  {
  $CI->$classvar = new $name;
  }
  }
  // --------------------------------------------------------------------
  /**
• 自动加载器
• autoload.PHP配置的自动加载文件有：
• | 1. Packages
  | 2. Libraries
  | 3. Helper files
  | 4. Custom config files
  | 5. Language files
  | 6. Models
  */
  private function _ci_autoloader()
  {
  if (defined('ENVIRONMENT') AND file_exists(APPPATH.'config/'.ENVIRONMENT.'/autoload.PHP'))
  {
  include(APPPATH.'config/'.ENVIRONMENT.'/autoload.PHP');
  }
  else
  {
  include(APPPATH.'config/autoload.PHP');
  }
  if ( ! isset($autoload))
  {
  return FALSE;
  }
  // 自动加载packages,也就是将package_path加入到library，model，helper，config
  if (isset($autoload['packages']))
  {
  foreach ($autoload['packages'] as $package_path)
  {
  $this->add_package_path($package_path);
  }
  }
  // 加载config文件
  if (count($autoload['config']) > 0)
  {
  $CI =& get_instance();
  foreach ($autoload['config'] as $key => $val)
  {
  $CI->config->load($val);
  }
  }
  // 加载helper和language
  foreach (array('helper','language') as $type)
  {
  if (isset($autoload[$type]) AND count($autoload[$type]) > 0)
  {
  $this->$type($autoload[$type]);
  }
  }
  // 这个好像是为了兼容以前版本的
  if ( ! isset($autoload['libraries']) AND isset($autoload['core']))
  {
  $autoload['libraries'] = $autoload['core'];
  }
  // 加载libraries
  if (isset($autoload['libraries']) AND count($autoload['libraries']) > 0)
  {
  // 加载db
  if (in_array('database',$autoload['libraries']))
  {
  $this->database();
  $autoload['libraries'] = array_diff($autoload['libraries'],array('database'));
  }
  // 加载所有其他libraries
  foreach ($autoload['libraries'] as $item)
  {
  $this->library($item);
  }
  }
  // Autoload models
  if (isset($autoload['model']))
  {
  $this->model($autoload['model']);
  }
  }
  // --------------------------------------------------------------------
  /**
• 返回由对象属性组成的关联数组
  */
  protected function _ci_object_to_array($object)
  {
  return (is_object($object)) ? get_object_vars($object) : $object;
  }
  // --------------------------------------------------------------------
  /**
• 获取CI某个组件的实例
  */
  protected function &_ci_get_component($component)
  {
  $CI =& get_instance();
  return $CI->$component;
  }
  // --------------------------------------------------------------------
  /**
• 处理文件名，这个函数主要是返回正确文件名
  */
  protected function _ci_prep_filename($filename,$extension)
  {
  if ( ! is_array($filename))
  {
  return array(strtolower(str_replace('.PHP',str_replace($extension,$filename)).$extension));
  }
  else
  {
  foreach ($filename as $key => $val)
  {
  $filename[$key] = strtolower(str_replace('.PHP',$val)).$extension);
  }
  return $filename;
  }
  }
  }