Magento: Update cart quantity programmatically - php

Question

I am creating a magento extension. In which I want to update the item quantity in cart programmatically. I am using the following code to display the items in cart.
$quote = Mage::getSingleton('checkout/session')->getQuote();
$cartItems = $quote->getAllVisibleItems();
foreach ($cartItems as $item) {
//Do something
}
What i want is to update the quantity on cart for a specific product. I know it can be done like this
$pid=15;
$quote = Mage::getSingleton('checkout/session')->getQuote();
$cartItems = $quote->getAllVisibleItems();
foreach ($cartItems as $item) {
if($pid==$item->getId())
$item->setQty($qty);
}
But I don't like this method as it would go through each and every product to update the quantity of a single product. I wonder if there is a way to update the quantity in one line i:e without using for loop.

Answer 1

You have the product_id, not the item_id right ?
If it's the case it's impossible to get the product id without performing the whole items.
Look at Mage_Sales_Model_Quote::getItemByProduct($product); you'll see it performs the whole catalog.
Basically I'll do it like this :
//get Product
$product = Mage::getModel('catalog/product')->load($pid);
//get Item
$item = $quote->getItemByProduct($product);
$quote->getCart()->updateItem(array($item->getId()=>array('qty'=>$qty)));
$quote->getCart()->save();
You should optimise this with some quick tricks :
$quote->hasProductId($pid) to check if product is in the cart
and
($qty!=$item->getQty())
to check if quantity is not already good...
Please note that it is untested code, and some kind of reflexions to help you find the solution, I didn't do the job for you.
Kind Regards,

Answer 2

I am sure it will work. Try this. It's save's my time.
public function updateCartAction(){
$item_id = $this->getRequest()->getParam('item_id');
$qty = $this->getRequest()->getParam('qty');
$quote = Mage::getSingleton('checkout/session')->getQuote();
$quote->updateItem($item_id, array( 'qty' => $qty));
$quote->save();
echo "Sssssss";
}

Answer 3

another solution
$quote = Mage::getModel('sales/quote')->setStoreId($storeId)->load($cartid);
$cartItems = $quote->getAllItems();
foreach ($cartItems as $item) {
if($cartiemid==$item->getId()){
$item->setQty($qty);
$item->save(); // you need to save the item after qty update
}
}
$quote->save();