Ajax Shoping Cart Items Update in Magento - magento

Question

I wrote here because I has been looking for way how to resolve my issue for 2h+ )
I need in updating shopping cart in Magento. There are similar questions at StackOverFlow.com but They looks not appropriate to my task
Let me explain shortly
1) I overwrote Mage_Checkout_CartController
like
class IB_Ajax_IndexController extends Mage_Checkout_CartController
It works nice with ajax adding products
for updating I send request
/ajax/index/updatePost
with params
form_key=H7XpKxwBOWQCkIHk&cart[304][qty]=39&cart[305][qty]=1&cart[306][qty]=1&update_cart_action=upd
It goes to my controller "IB_Ajax_IndexController"
which has all methods "Mage_Checkout_CartController"
I detected that this method does update
public function updatePostAction()
and then some update go to $this->_updateShoppingCart(); in above method
case 'update_qty':
$this->_updateShoppingCart();
break;
I copied its code to my controller for rewriting it here )
and I encountered so much difficult with it
how to detect SUCCESS or ERROR in this method updatePostAction() after execution $this->_updateShoppingCart() in it (
????
Maybe someone has experience with updating shopping cart via ajax ?
and how to modify above methods
Thanks a lot in advance

Answer 1

First make an response array like this.
$response = array();
After add cart code like $cart->save();
try{ if (!$cart->getQuote()->getHasError()){
$message = $this->__('%s was added to your shopping cart.', Mage::helper('core')->htmlEscape($product->getName()));
$response['status'] = 'SUCCESS';
$response['message'] = $message;
}
} catch (Exception $e) {
$response['status'] = 'ERROR';
$response['message'] = $this->__('Cannot add the item to shopping cart.');
Mage::logException($e);
}
$this->getResponse()->setBody(Mage::helper('core')->jsonEncode($response));
return;
And when you get response, by $response['status'] you can fetch SUCCESS or ERROR.