Magento第三方模型覆蓋

Question

我試圖覆蓋第三方擴展模型（「Userprofile」功能）的一部分，以包含更多的列和調用來檢索新的信息。這是第三方的config.xml：

<models> 
      <marketplace> 
       <class>Webkul_Marketplace_Model</class> 
       <resourceModel>marketplace_mysql4</resourceModel> 
      </marketplace> 
      <marketplace_mysql4> 
       <class>Webkul_Marketplace_Model_Mysql4</class> 
       <entities> 
        <product> 
         <table>marketplace_product</table> 
        </product> 
        <userprofile> 
         <table>marketplace_userdata</table> 
        </userprofile> 
        <feedback> 
         <table>marketplace_datafeedback</table> 
        </feedback> 
        <saleperpartner> 
         <table>marketplace_saleperpartner</table> 
        </saleperpartner> 
        <saleslist> 
         <table>marketplace_saleslist</table> 
        </saleslist> 
       </entities> 
      </marketplace_mysql4> 
     </models> 

這是我自己的config.xml：

<models> 
      <zerobars_marketplacepayment> 
       <class>ZeroBars_Marketplacepayment_Model</class> 
     </zerobars_marketplacepayment> 


      <marketplace> 
       <rewrite> 
        <userprofile>ZeroBars_Marketplacepayment_Model_Userprofile</userprofile> 
       </rewrite> 
      </marketplace> 
      <marketplace_mysql4> 
       <rewrite> 
        <userprofile>ZeroBars_Marketplacepayment_Model_Mysql4_Userprofile</userprofile> 
        <userprofile_collection>ZeroBars_Marketplacepayment_Model_Mysql4_Userprofile_Collection</userprofile_collection> 
       </rewrite> 
      </marketplace_mysql4> 

     </models> 

我複製所有文件USERPROFILE到我的模型結構，正是因爲他們在原分機與我自己取代「市場」命名的除外：

<?php 
class ZeroBars_Marketplacepayment_Model_Userprofile extends Mage_Core_Model_Abstract 
{ 
    public function _construct() 
    { 
     parent::_construct(); 
     $this->_init('zerobars_marketplacepayment/userprofile'); 

    } 

    public function getPartnerProfileById($partnerId) { 
     $data = array(); 
     if ($partnerId != '') { 
      $collection = Mage::getModel('zerobars_marketplacepayment/userprofile')->getCollection(); 
      $collection->addFieldToFilter('mageuserid',array('eq'=>$partnerId)); 
      $user = Mage::getModel('customer/customer')->load($partnerId); 

.... 

但是我仍然得到一個「致命錯誤：調用一個成員函數getCollection（）在非OB ject in /home/devzerob/public_html/app/code/local/ZeroBars/Marketplacepayment/Model/Userprofile.php on line 14「

該錯誤源於PHP文件的$ collection行。我錯過了什麼？我需要在配置部分中進行任何重寫嗎？