Rewriting resource model

Question

I am trying to follow the answer of this question Avoiding memory exhaustion when updating product stock? to rewrite a resource model. I created a custom module and is activated in the back-office. Here is my config.xml:

<?xml version="1.0" encoding="UTF-8"?>

 <config>
            <modules>
               <Mymodule_Vendor>
                    <version>0.1.0</version>
                </Mymodule_Vendor_Vendor>
             </modules>

       <models>
            <vendor>
               <class>Mymodule_Vendor_Model</class>
              <resourceModel>vendor_cataloginventory_resource</resourceModel>
      </vendor>

 <cataloginventory_resource>
      <rewrite>
             <stock_item>Mymodule_Vendor_Model_CatalogInventory_Resource_Stock_Item</stock_item>
      </rewrite>
 </cataloginventory_resource>
       </models>

 </config>

When i do this :

$stockItem = Mage::getModel('cataloginventory/stock_item')->loadByProduct($product)->setData('is_in_stock', $quantity > 0 ? 1 : 0)->setQty($quantity);
$stockItem->getResource()->saveAttribute($stockItem,array('is_in_stock','qty'));

Directories structure : app/code/local/Mymodule/Vendor/: -Model/CatalogInventory/Resource/Stock : item.php -etc : config.xml

I get this error : Fatal error: Call to undefined method Mage_CatalogInventory_Model_Resource_Stock_Item::saveAttribute()

I solved the error but i got another one:

Fatal error: Call to a member function loadByProduct() on a non-object

when i try this :

     $quantity = 8;
     $product = Mage::getModel('catalog/product')->loadByAttribute('sku',$sku);
     $productId = $product->getId();
     $product = Mage::getModel('catalog/product')->load($productId);
     $stockItem = Mage::getModel('cataloginventory/stock_item')->loadByProduct($product)->setData('is_in_stock', $quantity > 0 ? 1 : 0)->setQty($quantity);
 $stockItem->getResource()->saveAttribute($stockItem,array('is_in_stock','qty');

I didn't one to create another question so i edited this one.

Answer 1

The directory structure you have above is incorrect for the models.

app/code/local/Vendor/CatalogInventory/Model/Resource/Stock/Item.php

CatalogInventory and Model were inverted in yours.

Magento can't find this in local so is trying to load Mage/CatalogInventory/... rather than Vendor/CatalogInventory.

Adding the Firegento Debugger plugin certainly helps to identify this sort of issue when creating new modules.

Answer 2

As its a rewrite and you're defining new resource models you should simply remove the entire <resourceModel> node.