Loader加载器是基于ci框架项目开发中用的最广泛的组件之一，它让开发者能够非常方便的加载model，library，config等类和文件。 相信熟悉的CI的朋友都知道autoload这个配置文件吧，只要把需要加载的model,libray,driver,helper,config等配置到相应的参数中，就可以实现自动加载，这个自动加载的奥秘就在Loader.php中
1.自动加载
自动加载是在Loader组件加载之后发生的，而Loader组件加载是在CI_Controller的构造函数中，如下CI_Controller构造函数的源码：
/**
* Class constructor
*
* @return void
*/
public function __construct()
{
self::$instance =& $this;
// Assign all the class objects that were instantiated by the
// bootstrap file (CodeIgniter.php) to local class variables
// so that CI can run as one big super object.
foreach (is_loaded() as $var => $class)
{
$this->$var =& load_class($class);
}
$this->load =& load_class('Loader', 'core');
$this->load->initialize();
log_message('info', 'Controller Class Initialized');
}
看一下Loader源码就知道$this->load->initialize();这个函数只有一句代码
/**
* Initializer
*
* @todo Figure out a way to move this to the constructor
* without breaking *package_path*() methods.
* @uses CI_Loader::_ci_autoloader()
* @used-by CI_Controller::__construct()
* @return void
*/
public function initialize()
{
$this->_ci_autoloader();
}
由此我们可知，自动加载是在控制器的被创建的时候发生的，那么自动加载具体是怎么实现的呢？这就要看_ci_autoloader函数的代码了：
/**
* CI Autoloader
*
* Loads component listed in the config/autoload.php file.
*
* @used-by CI_Loader::initialize()
* @return void
*/
protected function _ci_autoloader()
{
if (file_exists(APPPATH.'config/autoload.php'))
{
include(APPPATH.'config/autoload.php');
}
if (file_exists(APPPATH.'config/'.ENVIRONMENT.'/autoload.php'))
{
include(APPPATH.'config/'.ENVIRONMENT.'/autoload.php');
}
if ( ! isset($autoload))
{
return;
}
// Autoload packages
if (isset($autoload['packages']))
{
foreach ($autoload['packages'] as $package_path)
{
$this->add_package_path($package_path);
}
}
// Load any custom config file
if (count($autoload['config']) > 0)
{
foreach ($autoload['config'] as $val)
{
$this->config($val);
}
}
// Autoload helpers and languages
foreach (array('helper', 'language') as $type)
{
if (isset($autoload[$type]) && count($autoload[$type]) > 0)
{
$this->$type($autoload[$type]);
}
}
// Autoload drivers
if (isset($autoload['drivers']))
{
$this->driver($autoload['drivers']);
}
// Load libraries
if (isset($autoload['libraries']) && count($autoload['libraries']) > 0)
{
// Load the database driver.
if (in_array('database', $autoload['libraries']))
{
$this->database();
$autoload['libraries'] = array_diff($autoload['libraries'], array('database'));
}
// Load all other libraries
$this->library($autoload['libraries']);
}
// Autoload models
if (isset($autoload['model']))
{
$this->model($autoload['model']);
}
}
2.视图加载
/**
* View Loader
*
* Loads "view" files.
*
* @param string $view View name
* @param array $vars An associative array of data
* to be extracted for use in the view
* @param bool $return Whether to return the view output
* or leave it to the Output class
* @return object|string
*/
public function view($view, $vars = array(), $return = FALSE)
{
return $this->_ci_load(array('_ci_view' => $view, '_ci_vars' => $this->_ci_prepare_view_vars($vars), '_ci_return' => $return));
}
/**
* Internal CI Data Loader
*
* Used to load views and files.
*
* Variables are prefixed with _ci_ to avoid symbol collision with
* variables made available to view files.
*
* @used-by CI_Loader::view()
* @used-by CI_Loader::file()
* @param array $_ci_data Data to load
* @return object
*/
protected function _ci_load($_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]) ? $_ci_data[$_ci_val] : FALSE;
}
$file_exists = FALSE;
// Set the path to the requested file
if (is_string($_ci_path) && $_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 $_ci_view_file => $cascade)
{
if (file_exists($_ci_view_file.$_ci_file))
{
$_ci_path = $_ci_view_file.$_ci_file;
$file_exists = TRUE;
break;
}
if ( ! $cascade)
{
break;
}
}
}
if ( ! $file_exists && ! file_exists($_ci_path))
{
show_error('Unable to load the requested file: '.$_ci_file);
}
// This allows anything loaded using $this->load (views, files, etc.)
// to become accessible from within the Controller and Model functions.
$_ci_CI =& get_instance();
foreach (get_object_vars($_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 $this->load->vars()
* function or via the second parameter of this function. We'll merge
* the two types and cache them so that views that are embedded within
* other views can have access to these variables.
*/
empty($_ci_vars) OR $this->_ci_cached_vars = array_merge($this->_ci_cached_vars, $_ci_vars);
extract($this->_ci_cached_vars);
/*
* Buffer the output
*
* We buffer the output for two reasons:
* 1. Speed. You get a significant speed boost.
* 2. So that the final rendered template can be post-processed by
* the output class. Why do we need post processing? For one thing,
* in order to show the elapsed page load time. Unless we can
* intercept the content right before it's sent to the browser and
* then stop the timer it won't be accurate.
*/
ob_start();
// If the PHP installation does not support short tags we'll
// do a little string replacement, changing the short tags
// to standard PHP echo statements.
if ( ! is_php('5.4') && ! ini_get('short_open_tag') && 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('info', 'File loaded: '.$_ci_path);
// Return the file data if requested
if ($_ci_return === TRUE)
{
$buffer = ob_get_contents();
@ob_end_clean();
return $buffer;
}
/*
* Flush the buffer... or buff the flusher?
*
* In order to permit views to be nested within
* other views, we need to flush the content back out whenever
* we are beyond the first level of output buffering so that
* it can be seen and included properly by the first included
* template and any subsequent ones. Oy!
*/
if (ob_get_level() > $this->_ci_ob_level + 1)
{
ob_end_flush();
}
else
{
$_ci_CI->output->append_output(ob_get_contents());
@ob_end_clean();
}
return $this;
}
由以上源码可知：
1. 如果我们在自己的业务逻辑中打开了缓冲区，并且没有进行关闭的话，那么加载view的输出内容是不会经过output组件的。
- 这段代码其实有一个bug，如果我们在传入的$_ci_vars参数中有这样一个参数array(‘_ci_path’=>’xxx.php’，因为_ci_load函数会将_ci_vars数组的元素提取成一个$_ci_path=’xxx.php’的变量，那么原来保存着加载文件路径的$_ci_path变量就被覆盖掉了，这样的话，就有可能导致加载失败。