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codeigniter是如何实现钩子机制的?

时间:2021-07-01 10:21:17 帮助过:13人阅读

codeigniter是如何实现钩子机制的?,有需要的朋友可以参考下。


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:

  1. /**
  2. * CodeIgniter
  3. *
  4. * An open source application development framework for PHP 5.1.6 or newer
  5. *
  6. * @package CodeIgniter
  7. * @author EllisLab Dev Team
  8. * @copyright Copyright (c) 2008 - 2014, EllisLab, Inc.
  9. * @copyright Copyright (c) 2014 - 2015, British Columbia Institute of Technology (http://bcit.ca/)
  10. * @license http://codeigniter.com/user_guide/license.html
  11. * [url=home.php?mod=space&uid=17823]@LINK[/url] http://codeigniter.com
  12. * @since Version 1.0
  13. * @filesource
  14. */
  15. // ------------------------------------------------------------------------
  16. /**
  17. * CodeIgniter Hooks Class
  18. *
  19. * Provides a mechanism to extend the base system without hacking.
  20. *
  21. * @package CodeIgniter
  22. * @subpackage Libraries
  23. * @category Libraries
  24. * @author EllisLab Dev Team
  25. * @link http://codeigniter.com/user_guide/libraries/encryption.html
  26. */
  27. class CI_Hooks {
  28. /**
  29. * Determines wether hooks are enabled
  30. *
  31. * @var bool
  32. */
  33. var $enabled = FALSE;
  34. /**
  35. * List of all hooks set in config/hooks.php
  36. *
  37. * @var array
  38. */
  39. var $hooks = array();
  40. /**
  41. * Determines wether hook is in progress, used to prevent infinte loops
  42. *
  43. * @var bool
  44. */
  45. var $in_progress = FALSE;
  46. /**
  47. * Constructor
  48. *
  49. */
  50. function __construct()
  51. {
  52. $this->_initialize();
  53. log_message('debug', "Hooks Class Initialized");
  54. }
  55. // --------------------------------------------------------------------
  56. /**
  57. * Initialize the Hooks Preferences
  58. *
  59. * @access private
  60. * @return void
  61. */
  62. function _initialize()
  63. {
  64. $CFG =& load_class('Config', 'core');
  65. // If hooks are not enabled in the config file
  66. // there is nothing else to do
  67. if ($CFG->item('enable_hooks') == FALSE)
  68. {
  69. return;
  70. }
  71. // Grab the "hooks" definition file.
  72. // If there are no hooks, we're done.
  73. if (defined('ENVIRONMENT') AND is_file(APPPATH.'config/'.ENVIRONMENT.'/hooks.php'))
  74. {
  75. include(APPPATH.'config/'.ENVIRONMENT.'/hooks.php');
  76. }
  77. elseif (is_file(APPPATH.'config/hooks.php'))
  78. {
  79. include(APPPATH.'config/hooks.php');
  80. }
  81. if ( ! isset($hook) OR ! is_array($hook))
  82. {
  83. return;
  84. }
  85. $this->hooks =& $hook;
  86. $this->enabled = TRUE;
  87. }
  88. // --------------------------------------------------------------------
  89. /**
  90. * Call Hook
  91. *
  92. * Calls a particular hook
  93. *
  94. * @access private
  95. * @param string the hook name
  96. * @return mixed
  97. */
  98. function _call_hook($which = '')
  99. {
  100. if ( ! $this->enabled OR ! isset($this->hooks[$which]))
  101. {
  102. return FALSE;
  103. }
  104. if (isset($this->hooks[$which][0]) AND is_array($this->hooks[$which][0]))
  105. {
  106. foreach ($this->hooks[$which] as $val)
  107. {
  108. $this->_run_hook($val);
  109. }
  110. }
  111. else
  112. {
  113. $this->_run_hook($this->hooks[$which]);
  114. }
  115. return TRUE;
  116. }
  117. // --------------------------------------------------------------------
  118. /**
  119. * Run Hook
  120. *
  121. * Runs a particular hook
  122. *
  123. * @access private
  124. * @param array the hook details
  125. * @return bool
  126. */
  127. function _run_hook($data)
  128. {
  129. if ( ! is_array($data))
  130. {
  131. return FALSE;
  132. }
  133. // -----------------------------------
  134. // Safety - Prevents run-away loops
  135. // -----------------------------------
  136. // If the script being called happens to have the same
  137. // hook call within it a loop can happen
  138. if ($this->in_progress == TRUE)
  139. {
  140. return;
  141. }
  142. // -----------------------------------
  143. // Set file path
  144. // -----------------------------------
  145. if ( ! isset($data['filepath']) OR ! isset($data['filename']))
  146. {
  147. return FALSE;
  148. }
  149. $filepath = APPPATH.$data['filepath'].'/'.$data['filename'];
  150. if ( ! file_exists($filepath))
  151. {
  152. return FALSE;
  153. }
  154. // -----------------------------------
  155. // Set class/function name
  156. // -----------------------------------
  157. $class = FALSE;
  158. $function = FALSE;
  159. $params = '';
  160. if (isset($data['class']) AND $data['class'] != '')
  161. {
  162. $class = $data['class'];
  163. }
  164. if (isset($data['function']))
  165. {
  166. $function = $data['function'];
  167. }
  168. if (isset($data['params']))
  169. {
  170. $params = $data['params'];
  171. }
  172. if ($class === FALSE AND $function === FALSE)
  173. {
  174. return FALSE;
  175. }
  176. // -----------------------------------
  177. // Set the in_progress flag
  178. // -----------------------------------
  179. $this->in_progress = TRUE;
  180. // -----------------------------------
  181. // Call the requested class and/or function
  182. // -----------------------------------
  183. if ($class !== FALSE)
  184. {
  185. if ( ! class_exists($class))
  186. {
  187. require($filepath);
  188. }
  189. $HOOK = new $class;
  190. $HOOK->$function($params);
  191. }
  192. else
  193. {
  194. if ( ! function_exists($function))
  195. {
  196. require($filepath);
  197. }
  198. $function($params);
  199. }
  200. $this->in_progress = FALSE;
  201. return TRUE;
  202. }
  203. }
  204. // END CI_Hooks class
  205. /* End of file Hooks.php */
  206. /* 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。

如何实现, codeigniter

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