Override PaymentExtensionInterface

Question

I'm trying to add a new field via KO in the payment method where paymentdata is collected. Right now all I see is the agreement_id as part of it's parameter. Now I added another parameter which is the subscription_id. But upon clicking the proceed button it say

Property "SubscriptionIds" does not have accessor method "getSubscriptionIds" in class "Magento\Quote\Api\Data\PaymentExtensionInterface".

Now I can't find this class in vendor/magento/module-quote/Api/Data. I need to overwrite this class right now it's being defined in the generated folder the content is this

<?php
namespace Magento\Quote\Api\Data;

/**
 * Extension class for @see \Magento\Quote\Api\Data\PaymentInterface
 */
class PaymentExtension extends \Magento\Framework\Api\AbstractSimpleObject implements PaymentExtensionInterface
{
    /**
     * @return string[]|null
     */
    public function getAgreementIds()
    {
        return $this->_get('agreement_ids');
    }

    /**
     * @param string[] $agreementIds
     * @return $this
     */
    public function setAgreementIds($agreementIds)
    {
        $this->setData('agreement_ids', $agreementIds);
        return $this;
    }
}

But I can't find this in the vendor folder even though I looked in the vendor/magento/module-quote/Api/Data

Any idea on how to override this? As I need to retrieve the new parameter when submitting the order in the payment method page

Answer 1

First of all, you cannot override PaymentExtensionInterface - it is generated piece of code.

If you want to define a new field, similar to agreement_ids you should create extension_attributes.xml file in your Company/Module/etc directory with a content like this:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Api/etc/extension_attributes.xsd">
    <extension_attributes for="Magento\Quote\Api\Data\PaymentInterface">
        <attribute code="subscription_id" type="string" />
    </extension_attributes>
</config>

Getters and setters for subscribtion_id attribute will be generated by Magento and will be present in PaymentExtensionInterface.

You can find more info here: https://devdocs.magento.com/guides/v2.3/howdoi/checkout/checkout_new_field.html

Unfortunately, example in docs is more about shipping than billing step form, but take a look at Magento's checkout-agreements module for some ideas.