Magento：从视图调用产品模型方法

Question

I've created a custom model to override core's Product Model.

// app/code/local/Commerce121/Catalog/Model/Product.php

include('Mage/Catalog/Model/Product.php');

class Commerce121_Catalog_Model_Product extends Mage_Catalog_Model_Product
{

  public function getCompatibilityGrid()
  {
        return '<table width="100%"><tr><th>Year</th><th>Model</th><tr>Engine</tr></tr></table>';
  }

}

// app/code/local/Commerce121/Catalog/etc/config.xml
<?xml version="1.0"?>
<config>
    <modules>
       <Commerce121_catalog>
            <version>1.0</version>
       </Commerce121_catalog>
   </modules>
   <global>
      <models>
       <catalog>
         <rewrite>
           <product>Commerce121_Catalog_Model_Product</product>
         </rewrite>
        </catalog>
      </models>
   </global>
</config>

// app/etc/modules/Commerce121_Catalog.xml
<?xml version="1.0"?>
<config>
    <modules>
        <Commerce121_catalog>
            <active>true</active>
            <codepool>local</codepool>
        </Commerce121_catalog>
    </modules>
</config>

In the admin the module is listed as enabled.

In app/design/frontend/.../default/template/catalog/product/view/view.phtml

I added:

echo $_product->getCompatibilityGrid();

But nothing shows (this is the view, since echo 'bla' shows). Is $_product a reference to a controller? If so, should I need to extend the controller as well?

Answer 1

Turs out Product model wasn't overriden. There was a part missing in the config.xml which declares the module:

<commerce121_catalog>
  <class>Commerce121_Catalog_Model</class>
</commerce121_catalog>

Should be like this:

<?xml version="1.0"?>
<config>
  <modules>
      <Commerce121_Catalog>
          <version>0.1.0</version>
      </Commerce121_Catalog>
  </modules>
  <global>
      <models>
        <commerce121_catalog>
            <class>Commerce121_Catalog_Model</class>
        </commerce121_catalog>
        <catalog>
          <rewrite>
            <product>Commerce121_Catalog_Model_Product</product>
          </rewrite>
        </catalog>
      </models>
  </global>
</config>