CodeIgniter框架钩子机制实现方法【hooks类】

本文实例讲述了CodeIgniter框架钩子机制实现方法。分享给大家供大家参考，具体如下：

记得上一次去到喜啦面试，面试官问我一个问题：codeigniter是如何实现钩子机制的？

当时答不上来，后来回来之后查了一些资料才明白，所以在这里记录一下：

codeigniter的钩子是这样实现的：首先在框架的核心文件PHP文件的 122行，载入Hooks类，接着在该文件中定义了几个挂载点，比如pre_system（129行）、post_controller_constructor（295行）等，并在这些挂载点上面执行hooks类的_call_hook() 方法。

另附codeigniter的hooks类的源代码：

PHP;"> // ------------------------------------------------------------------------

/**

CodeIgniter Hooks Class
Provides a mechanism to extend the base system without hacking.
@package CodeIgniter
@subpackage Libraries
@category Libraries
@author EllisLab Dev Team
@link http://codeigniter.com/user_guide/libraries/encryption.html
*/
class CI_Hooks {

/**

Determines wether hooks are enabled
@var bool
*/
var $enabled = FALSE;
/**
List of all hooks set in config/hooks.php
@var array
*/
var $hooks = array();
/**
Determines wether hook is in progress,used to prevent infinte loops
@var bool
*/
var $in_progress = FALSE;

/**

Constructor
*/
function __construct()
{
$this->_initialize();
log_message('debug',"Hooks Class Initialized");
}

// --------------------------------------------------------------------

/**

Initialize the Hooks Preferences
@access private
@return void
*/
function _initialize()
{
$CFG =& load_class('Config','core');

// If hooks are not enabled in the config file
// there is nothing else to do

if ($CFG->item('enable_hooks') == FALSE)
{
  return;
}

// Grab the "hooks" definition file.
// If there are no hooks,we're done.

if (defined('ENVIRONMENT') AND is_file(APPPATH.'config/'.ENVIRONMENT.'/hooks.<a href="/tag/PHP/" target="_blank" class="keywords">PHP</a>'))
{
  include(APPPATH.'config/'.ENVIRONMENT.'/hooks.<a href="/tag/PHP/" target="_blank" class="keywords">PHP</a>');
}
elseif (is_file(APPPATH.'config/hooks.<a href="/tag/PHP/" target="_blank" class="keywords">PHP</a>'))
{
  include(APPPATH.'config/hooks.<a href="/tag/PHP/" target="_blank" class="keywords">PHP</a>');
}


if ( ! isset($hook) OR ! is_array($hook))
{
  return;
}

$this->hooks =& $hook;
$this->enabled = TRUE;

}

// --------------------------------------------------------------------

/**

Call Hook
Calls a particular hook
@access private
@param string the hook name
@return mixed
*/
function _call_hook($which = '')
{
if ( ! $this->enabled OR ! isset($this->hooks[$which]))
{
return FALSE;
}

if (isset($this->hooks[$which][0]) AND is_array($this->hooks[$which][0]))
{
  foreach ($this->hooks[$which] as $val)
  {
    $this->_run_hook($val);
  }
}
else
{
  $this->_run_hook($this->hooks[$which]);
}

return TRUE;

}

// --------------------------------------------------------------------

/**

Run Hook
Runs a particular hook
@access private
@param array the hook details
@return bool
*/
function _run_hook($data)
{
if ( ! is_array($data))
{
return FALSE;
}

// -----------------------------------
// Safety - Prevents run-away loops
// -----------------------------------

// If the script being called happens to have the same
// hook call within it a loop can happen

if ($this->in_progress == TRUE)
{
  return;
}

// -----------------------------------
// Set file path
// -----------------------------------

if ( ! isset($data['filepath']) OR ! isset($data['filename']))
{
  return FALSE;
}

$filepath = APPPATH.$data['filepath'].'/'.$data['filename'];

if ( ! file_exists($filepath))
{
  return FALSE;
}

// -----------------------------------
// Set class/function name
// -----------------------------------

$class   = FALSE;
$function = FALSE;
$params    = '';

if (isset($data['class']) AND $data['class'] != '')
{
  $class = $data['class'];
}

if (isset($data['function']))
{
  $function = $data['function'];
}

if (isset($data['params']))
{
  $params = $data['params'];
}

if ($class === FALSE AND $function === FALSE)
{
  return FALSE;
}

// -----------------------------------
// Set the in_progress flag
// -----------------------------------

$this->in_progress = TRUE;

// -----------------------------------
// Call the requested class and/or function
// -----------------------------------

if ($class !== FALSE)
{
  if ( ! class_exists($class))
  {
    require($filepath);
  }

  $HOOK = new $class;
  $HOOK->$function($params);
}
else
{
  if ( ! function_exists($function))
  {
    require($filepath);
  }

  $function($params);
}

$this->in_progress = FALSE;
return TRUE;

}

// END CI_Hooks class

/ End of file Hooks.PHP /
/ Location: ./system/core/Hooks.PHP /

可以看出codeigniter实现钩子机制的方式不够优雅，其实完全可以使用观察者模式来实现钩子机制，将挂载点当做监听的事件。

更多关于CodeIgniter相关内容感兴趣的读者可查看本站专题：《》、《》、《》、《》、《》、《》、《》、《》及《PHP常见数据库操作技巧汇总》

希望本文所述对大家基于CodeIgniter框架的PHP程序设计有所帮助。

CodeIgniter框架钩子机制实现方法【hooks类】

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