我在 Magento 2 中创建了新表，用于存储自定义 promorules，现在我为事件创建了观察者，controller_action_predispatch_checkout_cart_couponPost并且在该观察者中我想检查用户是否输入了任何自定义规则，然后根据该规则应用折扣。
下面是我的代码：
<?php
namespace Webkul\Grid\Observer;
use Magento\Framework\Event\ObserverInterface;
class coupenAppliedAfter implements ObserverInterface
{
/**
* @var ObjectManagerInterface
*/
protected $_objectManager;
/**
* @param \Magento\Framework\ObjectManagerInterface $objectManager
*/
public function __construct(
\Magento\Framework\ObjectManagerInterface $objectManager
) {
$this->_objectManager = $objectManager;
}
/**
* customer register event handler
*
* @param \Magento\Framework\Event\Observer $observer
* @return void
*/
public function execute(\Magento\Framework\Event\Observer $observer)
{
// get enetered coupen code
$controller = $observer->getControllerAction();
$couponCode = $controller->getRequest()->getParam('coupon_code');
$objectManager = \Magento\Framework\App\ObjectManager::getInstance();
$connection = $objectManager->get('Magento\Framework\App\ResourceConnection')->getConnection('\Magento\Framework\App\ResourceConnection::DEFAULT_CONNECTION');
// get list of coupon codes from that custom table
$all_custom_codes = $connection->fetchAll("SELECT * FROM custom_promotion_rules");
foreach($all_custom_codes as $code) {
$db_coupen_code = $code['code'];
// matching if user has entered any custom code
if($couponCode == $db_coupen_code) {
// if yes trying to apply custom discount
$DiscountAmount = $code['discount_amount'];
$result = $observer->getEvent()->getResult();
$result->setAmount($DiscountAmount);
$result->setBaseAmount($DiscountAmount);
}
}
}
}
但上面的代码不起作用并给出错误Fatal error: Uncaught Error: Call to a member function setAmount() on null
请为此提出解决方案。