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

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：

<?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。