ZendFramework动作助手(Zend_Controller_Action_Helper)用法详解_PHP

通过助手模式，可以把一些经常使用的功能模块做封装，从而在可以在需要的地方灵活使用，主要是在action使用。

Zend Framework中有两种助手，动作助手(Zend_Controller_Action_Helper)和试图助手(Zend_View_Helper)。

动作助手可以向任何Zend_Controller_Action的衍生动作控制器中，即时的加入功能(runtime and/or on-demand functionality)，以使得增加公共的动作控制器功能时，尽量减少衍生动作控制器类的必要。

动作助手在需要调用时加载，可以在请求的时候(bootstrap)或者动作控制器创建的时候(init())实例化。

涉及到的相关文件

在/library/Zend/Controller/Action/中

│ Exception.php
│ HelperBroker.php
│ Interface.php
│
├─Helper
│ │ Abstract.php
│ │ ActionStack.php
│ │ AjaxContext.php
│ │ AutoCompleteDojo.php
│ │ AutoCompleteScriptaculous.php
│ │ Cache.php
│ │ ContextSwitch.php
│ │ FlashMessenger.php
│ │ Json.php
│ │ Redirector.php
│ │ Url.php
│ │ ViewRenderer.php
│ │
│ └─AutoComplete
│ Abstract.php
│
└─HelperBroker
PriorityStack.php

常见的动作助手有：

FlashMessenger 用来处理Flash Messenger会话；
Json 用来解码和发送 JSON 响应；
Url 用于创建Urls；
Redirector 提供另一种实现方式，帮助程序重定向到内部或者外部页面；
ViewRenderer 自动的完成在控制器内建立视图对象并渲染视图的过程；
AutoComplete 自动响应 AJAX 的自动完成；
ContextSwitch 和 AjaxContext 为你的动作提供替代响应格式；
Cache 实现cache的相关操作；
ActionStack 用于操作动作堆栈。

动手的几种实例化使用方式

1.通过Zend_Controller_Action的 $_helper成员的getHelper()方法。直接调用getHelper()，传入助手的名称即可。

$redirector = $this->_helper->getHelper('Redirector');
//$redirector->getName();
$redirector->gotoSimple('index2');

2.直接通过访问的_helper助手的属性对应的助手对象。

$redirector = $this->_helper->Redirector;

Zend_Controller_Action_HelperBroker

中文名称译作"助手经纪人",顾名思义，是动作助手的中间人。

在动作的实例化使用的方式的第二种方式就是通过Zend_Controller_Action_HelperBroker的魔术方法__get()来实现的。

助手经纪人用于注册助手对象和助手路径以及获取助手等等功能。

Zend_Controller_Action_HelperBroker的实现以及常用方法列表

<&＃63;php
/**
 * @see Zend_Controller_Action_HelperBroker_PriorityStack
 */
require_once 'Zend/Controller/Action/HelperBroker/PriorityStack.php';
/**
 * @see Zend_Loader
 */
require_once 'Zend/Loader.php';
/**
 * @category  Zend
 * @package  Zend_Controller
 * @subpackage Zend_Controller_Action
 * @copyright Copyright (c) 2005-2011 Zend Technologies USA Inc. (http://www.zend.com)
 * @license  http://framework.zend.com/license/new-bsd   New BSD License
 */
class Zend_Controller_Action_HelperBroker
{
  /**
   * $_actionController - ActionController reference
   *
   * @var Zend_Controller_Action
   */
  protected $_actionController;
  /**
   * @var Zend_Loader_PluginLoader_Interface
   */
  protected static $_pluginLoader;
  /**
   * $_helpers - Helper array
   *
   * @var Zend_Controller_Action_HelperBroker_PriorityStack
   */
  protected static $_stack = null;
  /**
   * Set PluginLoader for use with broker
   *
   * @param Zend_Loader_PluginLoader_Interface $loader
   * @return void
   */
  public static function setPluginLoader($loader)
  {
    if ((null !== $loader) && (!$loader instanceof Zend_Loader_PluginLoader_Interface)) {
      require_once 'Zend/Controller/Action/Exception.php';
      throw new Zend_Controller_Action_Exception('Invalid plugin loader provided to HelperBroker');
    }
    self::$_pluginLoader = $loader;
  }
  /**
   * Retrieve PluginLoader
   *
   * @return Zend_Loader_PluginLoader
   */
  public static function getPluginLoader()
  {
    if (null === self::$_pluginLoader) {
      require_once 'Zend/Loader/PluginLoader.php';
      self::$_pluginLoader = new Zend_Loader_PluginLoader(array(
        'Zend_Controller_Action_Helper' => 'Zend/Controller/Action/Helper/',
      ));
    }
    return self::$_pluginLoader;
  }
  /**
   * addPrefix() - Add repository of helpers by prefix
   *
   * @param string $prefix
   */
  static public function addPrefix($prefix)
  {
    $prefix = rtrim($prefix, '_');
    $path  = str_replace('_', DIRECTORY_SEPARATOR, $prefix);
    self::getPluginLoader()->addPrefixPath($prefix, $path);
  }
  /**
   * addPath() - Add path to repositories where Action_Helpers could be found.
   *
   * @param string $path
   * @param string $prefix Optional; defaults to 'Zend_Controller_Action_Helper'
   * @return void
   */
  static public function addPath($path, $prefix = 'Zend_Controller_Action_Helper')
  {
    self::getPluginLoader()->addPrefixPath($prefix, $path);
  }
  /**
   * addHelper() - Add helper objects
   *
   * @param Zend_Controller_Action_Helper_Abstract $helper
   * @return void
   */
  static public function addHelper(Zend_Controller_Action_Helper_Abstract $helper)
  {
    self::getStack()->push($helper);
    return;
  }
  /**
   * resetHelpers()
   *
   * @return void
   */
  static public function resetHelpers()
  {
    self::$_stack = null;
    return;
  }
  /**
   * Retrieve or initialize a helper statically
   *
   * Retrieves a helper object statically, loading on-demand if the helper
   * does not already exist in the stack. Always returns a helper, unless
   * the helper class cannot be found.
   *
   * @param string $name
   * @return Zend_Controller_Action_Helper_Abstract
   */
  public static function getStaticHelper($name)
  {
    $name = self::_normalizeHelperName($name);
    $stack = self::getStack();
    if (!isset($stack->{$name})) {
      self::_loadHelper($name);
    }
    return $stack->{$name};
  }
  /**
   * getExistingHelper() - get helper by name
   *
   * Static method to retrieve helper object. Only retrieves helpers already
   * initialized with the broker (either via addHelper() or on-demand loading
   * via getHelper()).
   *
   * Throws an exception if the referenced helper does not exist in the
   * stack; use {@link hasHelper()} to check if the helper is registered
   * prior to retrieving it.
   *
   * @param string $name
   * @return Zend_Controller_Action_Helper_Abstract
   * @throws Zend_Controller_Action_Exception
   */
  public static function getExistingHelper($name)
  {
    $name = self::_normalizeHelperName($name);
    $stack = self::getStack();
    if (!isset($stack->{$name})) {
      require_once 'Zend/Controller/Action/Exception.php';
      throw new Zend_Controller_Action_Exception('Action helper "' . $name . '" has not been registered with the helper broker');
    }
    return $stack->{$name};
  }
  /**
   * Return all registered helpers as helper => object pairs
   *
   * @return array
   */
  public static function getExistingHelpers()
  {
    return self::getStack()->getHelpersByName();
  }
  /**
   * Is a particular helper loaded in the broker&＃63;
   *
   * @param string $name
   * @return boolean
   */
  public static function hasHelper($name)
  {
    $name = self::_normalizeHelperName($name);
    return isset(self::getStack()->{$name});
  }
  /**
   * Remove a particular helper from the broker
   *
   * @param string $name
   * @return boolean
   */
  public static function removeHelper($name)
  {
    $name = self::_normalizeHelperName($name);
    $stack = self::getStack();
    if (isset($stack->{$name})) {
      unset($stack->{$name});
    }
    return false;
  }
  /**
   * Lazy load the priority stack and return it
   *
   * @return Zend_Controller_Action_HelperBroker_PriorityStack
   */
  public static function getStack()
  {
    if (self::$_stack == null) {
      self::$_stack = new Zend_Controller_Action_HelperBroker_PriorityStack();
    }
    return self::$_stack;
  }
  /**
   * Constructor
   *
   * @param Zend_Controller_Action $actionController
   * @return void
   */
  public function __construct(Zend_Controller_Action $actionController)
  {
    $this->_actiOnController= $actionController;
    foreach (self::getStack() as $helper) {
      $helper->setActionController($actionController);
      $helper->init();
    }
  }
  /**
   * notifyPreDispatch() - called by action controller dispatch method
   *
   * @return void
   */
  public function notifyPreDispatch()
  {
    foreach (self::getStack() as $helper) {
      $helper->preDispatch();
    }
  }
  /**
   * notifyPostDispatch() - called by action controller dispatch method
   *
   * @return void
   */
  public function notifyPostDispatch()
  {
    foreach (self::getStack() as $helper) {
      $helper->postDispatch();
    }
  }
  /**
   * getHelper() - get helper by name
   *
   * @param string $name
   * @return Zend_Controller_Action_Helper_Abstract
   */
  public function getHelper($name)
  {
    $name = self::_normalizeHelperName($name);
    $stack = self::getStack();
    if (!isset($stack->{$name})) {
      self::_loadHelper($name);
    }
    $helper = $stack->{$name};
    $initialize = false;
    if (null === ($actiOnController= $helper->getActionController())) {
      $initialize = true;
    } elseif ($actionController !== $this->_actionController) {
      $initialize = true;
    }
    if ($initialize) {
      $helper->setActionController($this->_actionController)
          ->init();
    }
    return $helper;
  }
  /**
   * Method overloading
   *
   * @param string $method
   * @param array $args
   * @return mixed
   * @throws Zend_Controller_Action_Exception if helper does not have a direct() method
   */
  public function __call($method, $args)
  {
    $helper = $this->getHelper($method);
    if (!method_exists($helper, 'direct')) {
      require_once 'Zend/Controller/Action/Exception.php';
      throw new Zend_Controller_Action_Exception('Helper "' . $method . '" does not support overloading via direct()');
    }
    return call_user_func_array(array($helper, 'direct'), $args);
  }
  /**
   * Retrieve helper by name as object property
   *
   * @param string $name
   * @return Zend_Controller_Action_Helper_Abstract
   */
  public function __get($name)
  {
    return $this->getHelper($name);
  }
  /**
   * Normalize helper name for lookups
   *
   * @param string $name
   * @return string
   */
  protected static function _normalizeHelperName($name)
  {
    if (strpos($name, '_') !== false) {
      $name = str_replace(' ', '', ucwords(str_replace('_', ' ', $name)));
    }
    return ucfirst($name);
  }
  /**
   * Load a helper
   *
   * @param string $name
   * @return void
   */
  protected static function _loadHelper($name)
  {
    try {
      $class = self::getPluginLoader()->load($name);
    } catch (Zend_Loader_PluginLoader_Exception $e) {
      require_once 'Zend/Controller/Action/Exception.php';
      throw new Zend_Controller_Action_Exception('Action Helper by name ' . $name . ' not found', 0, $e);
    }
    $helper = new $class();
    if (!$helper instanceof Zend_Controller_Action_Helper_Abstract) {
      require_once 'Zend/Controller/Action/Exception.php';
      throw new Zend_Controller_Action_Exception('Helper name ' . $name . ' -> class ' . $class . ' is not of type Zend_Controller_Action_Helper_Abstract');
    }
    self::getStack()->push($helper);
  }
}

助手经纪人的常见用法：

一、注册一个助手

1.

Zend_Controller_Action_HelperBroker::addHelper($helper);

2.通过addPrefix()方法带有一个类前缀参数，用来加入自定义助手类的路径。
要求前缀遵循Zend Framework的类命名惯例。

// Add helpers prefixed with My_Action_Helpers in My/Action/Helpers/
Zend_Controller_Action_HelperBroker::addPrefix('My_Action_Helpers');

3.使用addPath()方法第一个参数为一个目录，第二个为类前缀(默认为'Zend_Controller_Action_Helper')。

用来将自己的类前缀映射到指定的目录。

// Add helpers prefixed with Helper in Plugins/Helpers/
Zend_Controller_Action_HelperBroker::addPath('./Plugins/Helpers',
                       'Helper');

二、判读助手是否存在

使用hasHelper($name)方法来判定助手经纪人中是否存在某助手，$name是助手的短名称（去掉前缀的）：

// Check if 'redirector' helper is registered with the broker:
if (Zend_Controller_Action_HelperBroker::hasHelper('redirector')) {
  echo 'Redirector helper registered';
}

从助手经纪人中获取助手有两个静态方法：getExistingHelper() 和 getStaticHelper() 。getExistingHelper()将获取助手仅当它以前调用过或者显性地通过助手经纪人注册过，否则就抛出一个异常。getStaticHelper() 的做法和getExistingHelper()一样，但如果还没有注册助手堆栈，它将尝试初始化助手，为获取你要配置的的助手，getStaticHelper()是一个好的选择。

两个方法都带一个参数，$name，它是助手的短名称（去掉前缀）。

// Check if 'redirector' helper is registered with the broker, and fetch:
if (Zend_Controller_Action_HelperBroker::hasHelper('redirector')) {
  $redirector =
    Zend_Controller_Action_HelperBroker::getExistingHelper('redirector');
}
// Or, simply retrieve it, not worrying about whether or not it was
// previously registered:
$redirector =
  Zend_Controller_Action_HelperBroker::getStaticHelper('redirector');
}

三、removeHelper($name)删除助手经纪人中的某个助手，$name是助手的短名称。

// Conditionally remove the 'redirector' helper from the broker:
if (Zend_Controller_Action_HelperBroker::hasHelper('redirector')) {
  Zend_Controller_Action_HelperBroker::removeHelper('redirector')
}

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