Change scope for "Maximum Qty Allowed in Shopping Cart" in product

Question

Currently, for every product the attribute "Inventory" > "Maximum Qty Allowed in Shopping Cart" is defined in global scope for one article.

How can I change this scope to have the maximum quantity in the product defined for each webpage?

Everything I find is about changing the system configuration but does not affect the article: product[stock_data][max_sale_qty]

Answer 1

This field is stored in the table cataloginventory_stock_item which does not have a store_id field - so you basically could extend this table and adding a store ID.

Then you have to modify \Mage_CatalogInventory_Model_Stock_Item::getMaxSaleQty via a model rewrite.

In case you have the same max sale qty for all items of one store, it should work if you just modify the system configuration for max_sale_qty in app/code/core/Mage/CatalogInventory/etc/system.xml (also in a custom module with the same XML node)

   <max_sale_qty translate="label">
        <label>Maximum Qty Allowed in Shopping Cart</label>
        <frontend_type>text</frontend_type>
        <validate>validate-number</validate>
        <sort_order>4</sort_order>
        <show_in_default>1</show_in_default>
        <show_in_website>1</show_in_website>
        <show_in_store>1</show_in_store>
    </max_sale_qty>

Answer 2

I ended up writing a module that overwrites getMaxSaleQty() as needed. Ignoring the config value.

app/code/local/My/Modul/Model/Stock/Item.php

class My_Modul_Model_Stock_Item extends Mage_CatalogInventory_Model_Stock_Item
{
    public function getMaxSaleQty()
    {
        $max = parent::getMaxSaleQty();
        if (Mage::app()->getStore()->getStoreId() == 1)
        {
            if ($this->getProduct()->getFinalPrice() == 0)
            {
                $max = 1;
            }
        }
        return $max;
    }
}

and in app/code/local/My/Modul/etc/config.xml

<global>
    <models>
        <cataloginventory>
            <rewrite>
                <stock_item>My_Modul_Model_Stock_Item</stock_item>
            </rewrite>
        </cataloginventory>
    </models>
</global>

You could also add a custom attribute to control this.