Magento 1.9 - How to Override/Rewrite Third party Module?

Question

I am using this extension for Extra Fees,

I did some override/rewritein this file in magento (app/code/local/Voronoy/ExtraFee/Model/Quote/Address/Total/Fee/Rule.php).

FYI -> The override/rewrite function working.

I just create Observer for this extension :

My observer :

app/etc/modules/Gta_ExtraFeesRemove.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Gta_ExtraFeesRemove>
            <active>true</active>
            <codePool>local</codePool>
            <depends>
                <Voronoy_ExtraFee/>
            </depends>
        </Gta_ExtraFeesRemove>
    </modules>
</config>

app/code/local/Gta/ExtraFeesRemove/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Gta_ExtraFeesRemove>
        <version>0.1.0</version>
        </Gta_ExtraFeesRemove>
    </modules>
    <global>
        <models>
            <voronoy_extrafee>
                <rewrite>
<quote_address_total_fee_rule>Gta_ExtraFeesRemove_Model_Quote_AddressTotal_Fee_Rule</quote_address_total_fee_rule>
                </rewrite>
            </voronoy_extrafee>
        </models>
    </global>
</config>

app/code/local/Gta/ExtraFeesRemove/Model/Quote/AddressTotal/Fee/Rule.php

<?php


class Gta_ExtraFeesRemove_Model_Quote_AddressTotal_Fee_Rule extends Voronoy_ExtraFee_Model_Quote_Address_Total_Fee_Rule
{
    /**
     * Discount calculation object
     *
     * @var Mage_SalesRule_Model_Validator
     */
    protected $_calculator;
    /**
     * Initialize discount collector
     */
    public function __construct()
    {
        $this->_calculator = Mage::getSingleton('voronoy_extrafee/salesRule_validator');
    }
    /**
     * @param Mage_Sales_Model_Quote_Address $address
     *
     * @return Mage_Sales_Model_Quote_Address_Total_Abstract
     */
    public function collect(Mage_Sales_Model_Quote_Address $address)
    {
        if (!Mage::helper('voronoy_extrafee')->isRuleExtraFeeEnabled()) {
            return $this;
        }
        parent::collect($address);
        $quote = $address->getQuote();
        $shipping_method = $quote->getShippingAddress()->getShippingMethod();
        $current_website = Mage::app()->getWebsite()->getId();

        ### log ###
        Mage::log("ExtraFeesWebsite -".$current_website." website checking part");
        ### log ###


        /* Flat Rate Condition Start*/
        if ($shipping_method != 'flatrate' && $current_website != 2) :
            $store = Mage::app()->getStore($quote->getStoreId());
            $this->_calculator->reset($address);

            $items = $this->_getAddressItems($address);
            if (!count($items)) {
                return $this;
            }

            ### log ###
            Mage::log("FlatRateCondition - ".$items."Flat Rate Condition ");
            ### log ###

            $this->_calculator->init($store->getWebsiteId(), $quote->getCustomerGroupId(), $quote->getCouponCode());
            $this->_calculator->initTotals($items, $address);

            $items = $this->_calculator->sortItemsByPriority($items);
            foreach ($items as $item) {
                if ($item->getParentItemId()) {
                    continue;
                }
                if ($item->getHasChildren() && $item->isChildrenCalculated()) {
                    foreach ($item->getChildren() as $child) {
                        $this->_calculator->process($child);
                        $this->_addAmount($child->getExtraFeeRuleAmount());
                        $this->_addBaseAmount($child->getBaseExtraFeeRuleAmount());
                    }
                } else {
                    $this->_calculator->process($item);
                    $this->_addAmount($item->getExtraFeeRuleAmount());
                    $this->_addBaseAmount($item->getBaseExtraFeeRuleAmount());
                }
            }
            $this->_calculator->prepareDescription($address);

            ### log ###
            Mage::log("FlatRateCondition - ".$items."Flat Rate Condition ");
            ### log ###

        endif;
        // / Flat Rate Condition End /
    }
    /**
     * Fetch Totals
     *
     * @param Mage_Sales_Model_Quote_Address $address
     *
     * @return Voronoy_ExtraFee_Model_Quote_Address_Total_Fee_Rule
     */
    public function fetch(Mage_Sales_Model_Quote_Address $address)
    {
        if (!Mage::helper('voronoy_extrafee')->isRuleExtraFeeEnabled()) {
            return $this;
        }
        $amount = $address->getExtraFeeRuleAmount();
        if ($address->getExtraFeeRuleDescription()) {
            $discountLabel = Mage::helper('voronoy_extrafee')->__(
                '%s (%s)',
                Mage::helper('voronoy_extrafee')->getExtraFeeRuleLabel(),
                $address->getExtraFeeRuleDescription()
            );
        } else {
            $discountLabel = Mage::helper('voronoy_extrafee')->getExtraFeeRuleLabel();
        }
        if ($amount > 0) {
            $address->addTotal(array(
                'code' => $this->getCode(),
                'title' => $discountLabel,
                'value' => $amount
            ));
        }
        return $this;
    }


}

The observer for third party module not working.

FYI -> The changes in core working.

Answer 1

The correct way to override the Voronoy_ExtraFee_Model_Quote_Address_Total_Fee_Rule class in config.xml is

<?xml version="1.0"?>
<config>
    <modules>
        <Gta_ExtraFeesRemove>
        <version>0.1.0</version>
        </Gta_ExtraFeesRemove>
    </modules>
    <global>
        <models>
            <voronoy_extrafee>
                <rewrite>
<quote_address_total_fee_rule>Gta_ExtraFeesRemove_Model_Quote_AddressTotal_Fee_Rule</quote_address_total_fee_rule>
                </rewrite>
            </voronoy_extrafee>
        </models>
    </global>
</config>