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    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。

    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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