unsetting a custom shipping method

Question

I followed this tutorial to add some new shipping methods to my website

http://www.smashingmagazine.com/2014/01/15/create-custom-shipping-methods-magento/#more-130404

However i now need to disable these methods if an If statement is true. I already have the if statement which unsets the free shipping so i know that works. however i do seem to be able to unset the custom shipping methods. I know it is a long shot but does anyone know how i would go about this??

This is the IF statement i am using to unset free shipping if that helps

<?php if (($_shippingRateGroups = $this->getEstimateRates())): ?>
<form id="co-shipping-method-form" action="<?php echo $this->getUrl('checkout/cart/estimateUpdatePost') ?>">
                               <?php $quote = Mage::getSingleton('checkout/session')->getQuote();
                        $cartItems = $quote->getAllVisibleItems();
                        foreach ($cartItems as $item)
                    {
                        $productId = $item->getProductId();
                        $product = Mage::getModel('catalog/product')->load($productId);
                               if($product->getData('direct_delivery_product')==1){?>

                         <div class="direct_message">
                         <?php echo 'You have direct delivery products in your shopping cart. This means it may take longer than the standard 2-5 working days to deliver.';?></div>

                            <?php unset($_shippingRateGroups["freeshipping"]);
                             break;
                         }

                    }

                ?>

New collectRate method

public function collectRates(Mage_Shipping_Model_Rate_Request $request)
{
    //return nothing if the shipping method is disabled from config
    if (!$this->getConfigFlag('active')) {
        return false;
    }

    $productId = $item->getProductId();
                        $product = Mage::getModel('catalog/product')->load($productId);
                               if($product->getData('direct_delivery_product')==0){

         return false;
    }

    $result = Mage::getModel('shipping/rate_result');
        /* @var $result Mage_Shipping_Model_Rate_Result */

        $result->append($this->_getStandardShippingRate());
        $result->append($this->_getExpressShippingRate());

        return $result;
}

Thank you if you can help.

Answer 1

I assume you have a model associated to the shipping method.
In that module you must have a method called collectRates() that should return the costs of the available methods.
Just make your method look like this:

public function collectRates(Mage_Shipping_Model_Rate_Request $request)
{
    //return nothing if the shipping method is disabled from config
    if (!$this->getConfigFlag('active')) {
        return false;
    }
    //insert your logic here that determines if the method should be disabled
    //...and then
    if (your disable condition is met) {
         return false;
    }
    //rest of the code goes here
}

[EDIT]
The code you added does not work because the variable $item is not defined when you use it.
From your code I assume you want to not show the delivery method if at least one product in the cart has the value 0 for the attribute direct_delivery_product.
In case I'm right try this:

public function collectRates(Mage_Shipping_Model_Rate_Request $request)
{
    //return nothing if the shipping method is disabled from config
    if (!$this->getConfigFlag('active')) {
        return false;
    }
    $items = $request->getAllItems();
    foreach ($items as $item) {
        $productId = $item->getProductId();
        $product = Mage::getModel('catalog/product')->load($productId);
        if(!$product->getData('direct_delivery_product')){
            return false;
        }
    }
    //rest of your code here
}

Even if loading products in a loop is not the best practice, I think you should worry about optimizing later. This should make it work.