Manipulate package weight before shipping rates calculation

Question

I need to add some logic to weight package calculation before shipping rates are calculated. So I created a custom module with an observer on sales_quote_address_collect_totals_after event.

The observer looks like this

use Magento\Framework\Event\ObserverInterface;

class AfterCollectTotals implements ObserverInterface{

   public function execute(\Magento\Framework\Event\Observer $observer){


    foreach ($items as $item) {

         // My custom logic here to get the correct weight in $weight

    }
        $observer->getQuote()->getShippingAddress()->setWeight($weight);
    }
}

Weight appears to be set correctly, but when the Shipping Rates are calculated this value is ignored. In the carrier model, $request->getPackageWeight() returns the package weight before my manipulation.

Where am I wrong?

Thank you

Answer 1

I've find the solution.

I didn't have to use the observer but the right way is to override

class Shipping in Magento\Quote\Model\Quote\Address\Total

I added my custom logic to public function collect and my custom weight is used to calculate the shipping rates

Answer 2

Same problem. Im setting new weight on checkout_cart_product_add_after Event. Weight is set, but the shipping costs are wrong. How to recalculate the shipping costs? Has anyone some code snippes please?