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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system/core/codeiniter.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：
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<?php if ( ! defined('basepath')) exit('no direct script access allowed');
/**
* codeigniter
*
* an open source application development framework for php 5.1.6 or newer
*
* @package codeigniter
* @author ellislab dev team
* @copyright copyright (c) 2008 - 2014, ellislab, inc.
* @copyright copyright (c) 2014 - 2015, british columbia institute of technology (http://bcit.ca/)
* @license http://codeigniter.com/user_guide/license.html
* @link http://codeigniter.com
* @since version 1.0
* @filesource
*/
// ------------------------------------------------------------------------
/**
* 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.php'))
{
include(apppath.'config/'.environment.'/hooks.php');
}
elseif (is_file(apppath.'config/hooks.php'))
{
include(apppath.'config/hooks.php');
}
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：《codeigniter入门教程》、《ci(codeigniter)框架进阶教程》、《php优秀开发框架总结》、《thinkphp入门教程》、《thinkphp常用方法总结》、《zend framework框架入门教程》、《php面向对象程序设计入门教程》、《php+mysql数据库操作入门教程》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。
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