Mrthdrb

I have a Magento site where I need to remove some products from certain customer groups due to them having a zero price on the products.

I have tried catalog_product_collection_load_after event and have successfully managed to remove the products that I want. This however causes a gap on the catagory pages where the products would be. Would there be any way to go about remove products from a collection either before the pagination is set on the collection or to "remake" the collection once you've removed the products.

The code I've tried so far:

 /* Remove all products from the category list where the (group) price is zero */
public function removeZeroPriceProducts($observer) 

 if (! Mage::app()->getStore()->isAdmin())
 
 $collection = $observer->getEvent()->getCollection();
 //Loop through all products in the collection
 foreach ($collection as $product)
 $product->getFinalPrice() === 0)
 $observer->getEvent()->getCollection()->removeItemByKey($origProduct->getId());
 
 

Edit:
I've tried added it to _getProductCollection in List.php as suggested by Mohit.
This removes the product as expected but unfortunately still leaves a gap. I'll leave the code for that here as well.

protected function _getProductCollection()

 if (is_null($this->_productCollection)) 
 $layer = $this->getLayer();
 /* @var $layer Mage_Catalog_Model_Layer */
 if ($this->getShowRootCategory()) 
 $this->setCategoryId(Mage::app()->getStore()->getRootCategoryId());
 

 // if this is a product view page
 if (Mage::registry('product')) 
 // get collection of categories this product is associated with
 $categories = Mage::registry('product')->getCategoryCollection()
 ->setPage(1, 1)
 ->load();
 // if the product is associated with any category
 if ($categories->count()) 
 // show products from this category
 $this->setCategoryId(current($categories->getIterator()));
 
 

 $origCategory = null;
 if ($this->getCategoryId()) 
 $category = Mage::getModel('catalog/category')->load($this->getCategoryId());
 if ($category->getId()) 
 $origCategory = $layer->getCurrentCategory();
 $layer->setCurrentCategory($category);
 
 
 $this->_productCollection = $layer->getProductCollection();

 $this->prepareSortableFieldsByCategory($layer->getCurrentCategory());

 if ($origCategory) 
 $layer->setCurrentCategory($origCategory);
 
 

 //Try and remove a specific ID from the collection
 $collection = $this->_productCollection;
 $collection->removeItemByKey(4146);
 return $collection;

To modify product collection before rendering category page follow these steps:

1. Override MagentoCatalogBlockProductListProduct


2. In function _getProductCollection after if statement insert your code:

$collection = $this->_productCollection;
foreach ($collection as $k => $product)
 // Here goes your code to modify product
 // For example:

$collection->removeItemByKey($k);// Remove original item from collection 

$collection->setOrder('position','ASC');// Reorder collection as you want
return $collection;

I found a solution that seems to work.
On the customer_login event I loop through all the products and add all the products that the customer are not allowed to see into an array that I then save in a customer session variable.

I then create a function called removeZeroPriceProducts that catches onto the catalog_product_collection_load_before event. In this function I've excluded the products by doing the following:

/* Remove all products from the category list where the (group) price is zero */
public function removeZeroPriceProducts($observer) 

 if (! Mage::app()->getStore()->isAdmin())
 
 //Get all disallowed products for the user
 if($disallowed = Mage::getSingleton('checkout/session')->getDisallowedProducts())
 //Add a filter for the product collection that removes all the disallowed products
 $observer->getEvent()->getCollection()->addFieldToFilter('entity_id', array('nin' => $disallowed));
 
 

Instead of using removeItemByKey which removed the product but left a gap I now instead add a filter which removes all products that can be found in my session variable.

Note. I first tried to loop through all the products in the removeZeroPriceProducts fonction. This however broke the page which is why I instead added all the products to a session variable when the customer logs in