Fatal error: Call to a member function setFinalPrice() on a non-object? - magento

Question

When i installed an extension named ajax pro on magento 1.702. when i add a product to cart,it shows
Fatal error: Call to a member function setFinalPrice() on a non-object in ..app\code\core\Mage\Sales\Model\Quote\Item\Abstract.php on line 73.
although i delete all this extension's files and folders. when i add a product to cart. the error still exist? how to correct it. thank you. i have clear all the cache.

Answer 1

I got this error after programmatically creating a quote with a different store id to the default store id.
Fix was to run this sql (after backing up all sales_flat_quote tables, of course):
DELETE FROM sales_flat_quote_item;
Note that TRUNCATE sales_flat_quote_item won't work due to referential integrity, and that the above command will remove the linked records from some of the other sales_flat_quote tables as well.
In reply to the comment - if you don't have access to the database then ask your hosting provider to give it to you (most give you some sort of access - eg phpmyadmin) you can run it as a code snippet, I guess:
<?php
// Save this in Magento root directory.
require_once( dirname(__FILE__) . ' /app/Mage.php');
umask(0);
Mage::app()->setCurrentStore(0);
$resource = Mage::getSingleton('core/resource');
$dbw = $resource->getConnection('core_write');
$query = "DELETE FROM sales_flat_quote_item;";
$dbw->query($query);
It's not a good idea to run that on a live production system - existing customers will lose all the items in their carts - though if your site is broken and you've nothing left to lose, maybe give it a go!
To backup the database without access to it, https://www.phpmyadmin.net/ or a similar tool will help there. You can also run the above query directly using that.

Answer 2

Delete session files from var/session thats it.

Answer 3

If it is throwing for all the customers then you can delete sales_flat_quote_item table. If this happens only for particular customer then do the following thing. In this case, all the quotes wont be deleted.
Get the customer id from sales_flat_quote_address(column name: customer_id) table. Here you can get the specific quote id(column name in table is quote_id) which is causing the problem.
Example: SELECT quote_id FROM sales_flat_quote_address where customer_id=23423
Now, go to sales_flat_quote_item then delete the particular records which is causing the problem.
Example: DELETE FROM sales_flat_quote_item WHERE quote_id=43535