CI框架 -- 核心文件 之 Loader.php（加载器）
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顾名思义，装载器就是加载元素的，使用CI时，经常加载的有：
加载类库文件：$this->load->library()
加载视图文件：$this->load->view()
加载模型文件：$this->load->model()
加载数据库文件：$this->load->database()
加载帮助文件：$this->load->helper()
加载配置文件：$this->load->config()
加载包路径：$this->load->add_package_path()
源码：
1 /** 2 * Loader Class 3 * 4 * 用户加载views和files，常见的函数有model(),view(),library(),helper() 5 * 6 * Controller的好助手，$this->load =& load_class(‘Loader‘, ‘core‘);，加载了loader，Controller就无比强大了 7 * @link http://www.phpddt.com 8 */ 9 class CI_Loader { 10 11 protected $_ci_ob_level; 12 13 protected $_ci_view_paths = array(); 14 protected $_ci_library_paths = array(); 15 protected $_ci_model_paths = array(); 16 protected $_ci_helper_paths = array(); 17 18 protected $_base_classes = array(); // Set by the controller class 19 20 protected $_ci_cached_vars = array(); 21 22 protected $_ci_classes = array(); 23 24 protected $_ci_loaded_files = array(); 25 26 protected $_ci_models = array(); 27 28 protected $_ci_helpers = array(); 29 30 protected $_ci_varmap = array(‘unit_test‘ => ‘unit‘, 31 ‘user_agent‘ => ‘agent‘); 32 33 public function __construct() 34 { 35 //获取缓冲嵌套级别 36 $this->_ci_ob_level = ob_get_level(); 37 //library路径 38 $this->_ci_library_paths = array(APPPATH, BASEPATH); 39 //helper路径 40 $this->_ci_helper_paths = array(APPPATH, BASEPATH); 41 //model路径 42 $this->_ci_model_paths = array(APPPATH); 43 //view路径 44 $this->_ci_view_paths = array(APPPATH.‘views/‘ => TRUE); 45 46 log_message(‘debug‘, "Loader Class Initialized"); 47 } 48 49 // -------------------------------------------------------------------- 50 51 /** 52 * 初始化Loader 53 * 54 */ 55 public function initialize() 56 { 57 $this->_ci_classes = array(); 58 $this->_ci_loaded_files = array(); 59 $this->_ci_models = array(); 60 //将is_loaded（common中记录加载核心类函数）加载的核心类交给_base_classes 61 $this->_base_classes =& is_loaded(); 62 63 //加载autoload.php配置中文件 64 $this->_ci_autoloader(); 65 66 return $this; 67 } 68 69 // -------------------------------------------------------------------- 70 71 /** 72 * 检测类是否加载 73 */ 74 public function is_loaded($class) 75 { 76 if (isset($this->_ci_classes[$class])) 77 { 78 return $this->_ci_classes[$class]; 79 } 80 81 return FALSE; 82 } 83 84 // -------------------------------------------------------------------- 85 86 /** 87 * 加载Class 88 */ 89 public function library($library = ‘‘, $params = NULL, $object_name = NULL) 90 { 91 if (is_array($library)) 92 { 93 foreach ($library as $class) 94 { 95 $this->library($class, $params); 96 } 97 98 return; 99 } 100 101 //如果$library为空或者已经加载。。。 102 if ($library == ‘‘ OR isset($this->_base_classes[$library])) 103 { 104 return FALSE; 105 } 106 107 if ( ! is_null($params) && ! is_array($params)) 108 { 109 $params = NULL; 110 } 111 112 $this->_ci_load_class($library, $params, $object_name); 113 } 114 115 // -------------------------------------------------------------------- 116 117 /** 118 * 加载和实例化model 119 */ 120 public function model($model, $name = ‘‘, $db_conn = FALSE) 121 { 122 //CI支持数组加载多个model 123 if (is_array($model)) 124 { 125 foreach ($model as $babe) 126 { 127 $this->model($babe); 128 } 129 return; 130 } 131 132 if ($model == ‘‘) 133 { 134 return; 135 } 136 137 $path = ‘‘; 138 139 // 是否存在子目录 140 if (($last_slash = strrpos($model, ‘/‘)) !== FALSE) 141 { 142 // The path is in front of the last slash 143 $path = substr($model, 0, $last_slash + 1); 144 145 // And the model name behind it 146 $model = substr($model, $last_slash + 1); 147 } 148 149 if ($name == ‘‘) 150 { 151 $name = $model; 152 } 153 154 if (in_array($name, $this->_ci_models, TRUE)) 155 { 156 return; 157 } 158 159 $CI =& get_instance(); 160 if (isset($CI->$name)) 161 { 162 show_error(‘The model name you are loading is the name of a resource that is already being used: ‘.$name); 163 } 164 165 $model = strtolower($model); //model文件名全小写 166 167 foreach ($this->_ci_model_paths as $mod_path) 168 { 169 if ( ! file_exists($mod_path.‘models/‘.$path.$model.‘.php‘)) 170 { 171 continue; 172 } 173 174 if ($db_conn !== FALSE AND ! class_exists(‘CI_DB‘)) 175 { 176 if ($db_conn === TRUE) 177 { 178 $db_conn = ‘‘; 179 } 180 181 $CI->load->database($db_conn, FALSE, TRUE); 182 } 183 184 if ( ! class_exists(‘CI_Model‘)) 185 { 186 load_class(‘Model‘, ‘core‘); 187 } 188 189 require_once($mod_path.‘models/‘.$path.$model.‘.php‘); 190 191 $model = ucfirst($model); 192 193 $CI->$name = new $model(); 194 //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。 195 $this->_ci_models[] = $name; 196 return; 197 } 198 199 // couldn‘t find the model 200 show_error(‘Unable to locate the model you have specified: ‘.$model); 201 } 202 203 // -------------------------------------------------------------------- 204 205 /** 206 * 数据库Loader 207 */ 208 public function database($params = ‘‘, $return = FALSE, $active_record = NULL) 209 { 210 // Grab the super object 211 $CI =& get_instance(); 212 213 // 是否需要加载db 214 if (class_exists(‘CI_DB‘) AND $return == FALSE AND $active_record == NULL AND isset($CI->db) AND is_object($CI->db)) 215 { 216 return FALSE; 217 } 218 219 require_once(BASEPATH.‘database/DB.php‘); 220 221 if ($return === TRUE) 222 { 223 return DB($params, $active_record); 224 } 225 226 // Initialize the db variable. Needed to prevent 227 // reference errors with some configurations 228 $CI->db = ‘‘; 229 230 // Load the DB class 231 $CI->db =& DB($params, $active_record); 232 } 233 234 // -------------------------------------------------------------------- 235 236 /** 237 * 加载数据库工具类 238 */ 239 public function dbutil() 240 { 241 if ( ! class_exists(‘CI_DB‘)) 242 { 243 $this->database(); 244 } 245 246 $CI =& get_instance(); 247 248 // for backwards compatibility, load dbforge so we can extend dbutils off it 249 // this use is deprecated and strongly discouraged 250 $CI->load->dbforge(); 251 252 require_once(BASEPATH.‘database/DB_utility.php‘); 253 require_once(BASEPATH.‘database/drivers/‘.$CI->db->dbdriver.‘/‘.$CI->db->dbdriver.‘_utility.php‘); 254 $class = ‘CI_DB_‘.$CI->db->dbdriver.‘_utility‘; 255 256 $CI->dbutil = new $class(); 257 } 258 259 // -------------------------------------------------------------------- 260 261 /** 262 * Load the Database Forge Class 263 * 264 * @return string 265 */ 266 public function dbforge() 267 { 268 if ( ! class_exists(‘CI_DB‘)) 269 { 270 $this->database(); 271 } 272 273 $CI =& get_instance(); 274 275 require_once(BASEPATH.‘database/DB_forge.php‘); 276 require_once(BASEPATH.‘database/drivers/‘.$CI->db->dbdriver.‘/‘.$CI->db->dbdriver.‘_forge.php‘); 277 $class = ‘CI_DB_‘.$CI->db->dbdriver.‘_forge‘; 278 279 $CI->dbforge = new $class(); 280 } 281 282 // -------------------------------------------------------------------- 283 284 /** 285 * 加载视图文件 286 */ 287 public function view($view, $vars = array(), $return = FALSE) 288 { 289 return $this->_ci_load(array(‘_ci_view‘ => $view, ‘_ci_vars‘ => $this->_ci_object_to_array($vars), ‘_ci_return‘ => $return)); 290 } 291 292 // -------------------------------------------------------------------- 293 294 /** 295 * 加载普通文件 296 */ 297 public function file($path, $return = FALSE) 298 { 299 return $this->_ci_load(array(‘_ci_path‘ => $path, ‘_ci_return‘ => $return)); 300 } 301 302 // -------------------------------------------------------------------- 303 304 /** 305 * 设置变量 306 * 307 * Once variables are set they become available within 308 * the controller class and its "view" files. 309 * 310 */ 311 public function vars($vars = array(), $val = ‘‘) 312 { 313 if ($val != ‘‘ AND is_string($vars)) 314 { 315 $vars = array($vars => $val); 316 } 317 318 $vars = $this->_ci_object_to_array($vars); 319 320 if (is_array($vars) AND count($vars) > 0) 321 { 322 foreach ($vars as $key => $val) 323 { 324 $this->_ci_cached_vars[$key] = $val; 325 } 326 } 327 } 328 329 // -------------------------------------------------------------------- 330 331 /** 332 * 检查并获取变量 333 */ 334 public function get_var($key) 335 { 336 return isset($this->_ci_cached_vars[$key]) ? $this->_ci_cached_vars[$key] : NULL; 337 } 338 339 // -------------------------------------------------------------------- 340 341 /** 342 * 加载helper 343 */ 344 public function helper($helpers = array()) 345 { 346 foreach ($this->_ci_prep_filename($helpers, ‘_helper‘) as $helper) 347 { 348 if (isset($this->_ci_helpers[$helper])) 349 { 350 continue; 351 } 352 353 $ext_helper = APPPATH.‘helpers/‘.config_item(‘subclass_prefix‘).$helper.‘.php‘; 354 355 // 如果是扩展helper的话 356 if (file_exists($ext_helper)) 357 { 358 $base_helper = BASEPATH.‘helpers/‘.$helper.‘.php‘; 359 360 if ( ! file_exists($base_helper)) 361 { 362 show_error(‘Unable to load the requested file: helpers/‘.$helper.‘.php‘); 363 } 364 365 include_once($ext_helper); 366 include_once($base_helper); 367 368 $this->_ci_helpers[$helper] = TRUE; 369 log_message(‘debug‘, ‘Helper loaded: ‘.$helper); 370 continue; 371 } 372 373 // 如果不是扩展helper，helper路径中加载helper 374 foreach ($this->_ci_helper_paths as $path) 375 { 376 if (file_exists($path.‘helpers/‘.$helper.‘.php‘)) 377 { 378 include_once($path.‘helpers/‘.$helper.‘.php‘); 379 380 $this->_ci_helpers[$helper] = TRUE; 381 log_message(‘debug‘, ‘Helper loaded: ‘.$helper); 382 break; 383 } 384 } 385 386 // 如果该helper还没加载成功的话，说明加载helper失败 387 if ( ! isset($this->_ci_helpers[$helper])) 388 { 389 show_error(‘Unable to load the requested file: helpers/‘.$helper.‘.php‘); 390 } 391 } 392 } 393 394 // -------------------------------------------------------------------- 395 396 /** 397 * 可以看到helpers调用也是上面的helper,只是helpers的别名而已 398 */ 399 public function helpers($helpers = array()) 400 { 401 $this->helper($helpers); 402 } 403 404 // -------------------------------------------------------------------- 405 406 /** 407 * 加载language文件 408 */ 409 public function language($file = array(), $lang = ‘‘) 410 { 411 $CI =& get_instance(); 412 413 if ( ! is_array($file)) 414 { 415 $file = array($file); 416 } 417 418 foreach ($file as $langfile) 419 { 420 $CI->lang->load($langfile, $lang); 421 } 422 } 423 424 // -------------------------------------------------------------------- 425 426 /** 427 * 加载配置文件 428 */ 429 public function config($file = ‘‘, $use_sections = FALSE, $fail_gracefully = FALSE) 430 { 431 $CI =& get_instance(); 432 $CI->config->load($file, $use_sections, $fail_gracefully); 433 } 434 435 // -------------------------------------------------------------------- 436 437 /** 438 * Driver 439 * 440 * 加载 driver library 441 */ 442 public function driver($library = ‘‘, $params = NULL, $object_name = NULL) 443 { 444 if ( ! class_exists(‘CI_Driver_Library‘)) 445 { 446 // we aren‘t instantiating an object here, that‘ll be done by the Library itself 447 require BASEPATH.‘libraries/Driver.php‘; 448 } 449 450 if ($library == ‘‘) 451 { 452 return FALSE; 453 } 454 455 // We can save the loader some time since Drivers will *always* be in a subfolder, 456 // and typically identically named to the library 457 if ( ! strpo以上是关于CI框架 -- 核心文件 之 Loader.php（加载器）的主要内容，如果未能解决你的问题，请参考以下文章
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