Magento 1: best approach to change product prices on the fly

Question

So I have this requirement where I need to round product prices based on several criteria for one specific currency.

So when watching the catalog (category view / product view whatever) the prices need to be updated on the fly.

I managed to get it right by using the following observer:

<frontend>
    <events>
        <catalog_product_get_final_price>
            <observers>
                <update_price_on_the_fly>
                    <type>singleton</type>
                    <class>Vendor_Module_Model_Observer</class>
                    <method>roundPrice</method>
                </update_price_on_the_fly>
            </observers>
        </catalog_product_get_final_price>
    </events>
</frontend>

Then in my observer I did:

public function roundPrice(Varien_Event_Observer $observer) {

    // check if are using NZD conversion
    if (!preg_match("/NZD/i", $code = Mage::app()->getStore()->getCurrentCurrencyCode())) {
        return;
    }

    $newPrice = $this->_getPriceLogic($observer->getProduct());
    $observer->getProduct()->setFinalPrice($newPrice);
}

That works fine for the product view page but does not work on the category page. It seems like catalog_product_get_final_price event is not dispatched on the category page.

I tried to observer catalog_product_collection_load_after event and use the following code but it does not seem to work entirely.

Instead of displaying my rounded price is displays:

rounded price as low as original price

public function roundPriceCollection($observer) {

    // check if are using NZD conversion
    if (!preg_match("/NZD/i", $code = Mage::app()->getStore()->getCurrentCurrencyCode())) {
        return;
    }

    $event = $observer->getEvent();
    $products = $observer->getCollection();
    foreach( $products as $product ) {
        $product->setFinalPrice($this->_getPriceLogic($product));
    }
    return $this;
}

Thus I'm wondering what is the best approach to implement such feature.

Answer 1

Thanks to @Marius, @Vinai and @AndreasVonStudnitz here's how I managed to get it right.

So the catalog_product_get_final_price is only for display purpose on the product view page and the final price from the category and checkout pages come from the price index database table.

Thus I was right using catalog_product_collection_load_after

However, to fix the As Low As display issue I had to add the following code to my observer code:

$product->setPrice($this->_getPriceLogic($product));
$product->setMinimalPrice($this->_getPriceLogic($product));

Of course, as this was for a simple product not on sale it was an easy case and I'll probably have some adjustements to make in order to get it working for every case but I got the idea now.

Answer 2

A wild idea.
You say that it works for the product details page because the event catalog_product_get_final_price is triggered.
How about making it trigger in the list page?
The event is not triggered in the event page because the getFinalPrice method looks like this:

public function getFinalPrice($qty=null)
{
    $price = $this->_getData('final_price');
    if ($price !== null) {
        return $price;
    }
    return $this->getPriceModel()->getFinalPrice($qty, $this);
}

The event is dispatched in the method Mage_Catalog_Model_Product_Type_Price::getFinalPrice.
You can try to rewrite the method it means the getFinalPrice from the product model and skip the verification for $price = $this->_getData('final_price'); when the currency is NZD.
Or change it to something like

public function getFinalPrice($qty=null)
{
    $price = $this->_getData('my_final_price'); //change the attributehere
    if ($price !== null) {
        return $price;
    }
    return $this->getPriceModel()->getFinalPrice($qty, $this);
}

then rewrite the getFinalPrice method from Mage_Catalog_Model_Product_Type_Price and make sure it sets the value for my_custom_price also.
And in order to make sure you don't get in the list something like regular price / promo price apply your price logic to the price minimal_price and special_price and all other prices that might be involved in the price.phtml file.
I didn't test this, but it looks like it's worth a try.

Answer 3

For update pricing or any product attribute like name, description, you can use the event catalog_product_collection_load_after and php observer function would be like below.

public function priceupdate(Varien_Event_Observer $observer){ $products = $observer->getCollection(); foreach( $products as $product ) { $product->setMinimalPrice($priceincfriegt); $product->setPrice($priceincfriegt); } return $this; }