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
<?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?
*
* @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')
}
下面介绍如何自定义助手。