Magento 2 : Currency change frontend event

Question

I want to update the quote item price on switching the currency from the frontend.

Is there any event to track currency switch option and give me the previous currency and requested currency?

Answer 1

I would recommend to write a Plugin on the following Controller Action :

Magento\Directory\Controller\Currency\SwitchAction

For example:

    <?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">    
    <type name="Magento\Directory\Controller\Currency\Switch">
        <plugin name="yournamespace_yourmodule_directory_currency_switch_plugin" 
                type="YourNamespace\YourModule\Plugin\Magento\Direcotry\Controller\Currency\SwitchAction"
                sortOrder="10" 
                disabled="false"/>
    </type>
</config>

And then you could use the following code:

        <?php


    namespace YourNamespace\YourModule\Plugin\Magento\Directory\Controller\Currency;

    class SwitchAction
    {

        protected $storeManager;

        public function __construct(
               \Magento\Store\Model\StoreManagerInterface $storeManager
        ) {
            $this->storeManager= $storeManager;
        }

        public function beforeExecute(
            \Magento\Directory\Controller\Currency\SwitchAction $subject,
            $result
        ) {
            $currentCurrency = $this->storeManager->getStore()->getCurrentCurrencyCode();
            $newCurrency = (string)$this->getRequest()->getParam('currency');
            // your code here

        }
    }

Answer 2

[Magento Version 2.4.x]

app/code/VendorName/ModuleName/etc/frontend

di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Directory\Controller\Currency\SwitchAction">
        <plugin name="custom_action_on_currency_switch"
                type="VendorName\ModuleName\Plugin\Direcotry\Controller\Currency\SwitchAction"
                sortOrder="10"/>
    </type>
</config>

app/code/VendorName/ModuleName/Plugin/Direcotry/Controller/Currency

SwitchAction.php

<?php

namespace VendorName\ModuleName\Plugin\Direcotry\Controller\Currency;

use Magento\Directory\Controller\Currency\SwitchAction as SwitchActionParent;

class SwitchAction
{
    /**
     * Currency switcher before plugin
     *
     * @param SwitchActionParent $subject
     *
     * @return void
     */
    public function beforeExecute(SwitchActionParent $subject)
    {
        $newCurrency = (string) $subject->getRequest()->getParam('currency');
        echo "New Currency ".$newCurrency;
        // Add your code here.
    }
}