Magento 2下单触发致命错误跳转回购物车问题求助

这个致命错误的核心原因是你错误地在观察者的构造函数中注入了\Magento\Framework\Event\Observer实例，这完全违背了Magento 2观察者的工作机制：

Magento 2中，Observer对象是在事件触发时由框架动态创建并直接传递给execute()方法的，它不属于可以通过依赖注入容器提供的服务。你在构造函数里添加这个依赖后，DI容器无法正确解析并提供有效的Observer实例，最终导致调用execute()时传入了null，触发类型错误。

修复步骤 #

1. 移除错误的依赖注入：删掉构造函数中的\Magento\Framework\Event\Observer参数，以及对应的$_observer属性定义。
2. 恢复execute()方法的正确逻辑：直接使用方法参数传入的$observer对象，不要用构造函数中存储的无效实例覆盖它。

修复后的完整代码 #

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\SalesRule\Observer;

use Magento\Framework\Event\Observer;
use Magento\Framework\Event\ObserverInterface;

class SalesOrderAfterPlaceObserver implements ObserverInterface
{
    /**
     * @var \Magento\SalesRule\Model\RuleFactory
     */
    protected $_ruleFactory;

    /**
     * @var \Magento\SalesRule\Model\Rule\CustomerFactory
     */
    protected $_ruleCustomerFactory;

    /**
     * @var \Magento\SalesRule\Model\Coupon
     */
    protected $_coupon;

    /**
     * @var \Magento\SalesRule\Model\ResourceModel\Coupon\Usage
     */
    protected $_couponUsage;

    /**
     * @param \Magento\SalesRule\Model\RuleFactory $ruleFactory
     * @param \Magento\SalesRule\Model\Rule\CustomerFactory $ruleCustomerFactory
     * @param \Magento\SalesRule\Model\Coupon $coupon
     * @param \Magento\SalesRule\Model\ResourceModel\Coupon\Usage $couponUsage
     */
    public function __construct(
        \Magento\SalesRule\Model\RuleFactory $ruleFactory,
        \Magento\SalesRule\Model\Rule\CustomerFactory $ruleCustomerFactory,
        \Magento\SalesRule\Model\Coupon $coupon,
        \Magento\SalesRule\Model\ResourceModel\Coupon\Usage $couponUsage
    ) {
        $this->_ruleFactory = $ruleFactory;
        $this->_ruleCustomerFactory = $ruleCustomerFactory;
        $this->_coupon = $coupon;
        $this->_couponUsage = $couponUsage;
    }

    /**
     * @param Observer $observer
     * @return $this
     * @SuppressWarnings(PHPMD.CyclomaticComplexity)
     */
    public function execute(Observer $observer)
    {
        $order = $observer->getEvent()->getOrder();
        if (!$order || !$order->getAppliedRuleIds()) {
            return $this;
        }

        // lookup rule ids
        $ruleIds = explode(',', $order->getAppliedRuleIds());
        $ruleIds = array_unique($ruleIds);

        $ruleCustomer = null;
        $customerId = $order->getCustomerId();

        // use each rule (and apply to customer, if applicable)
        foreach ($ruleIds as $ruleId) {
            if (!$ruleId) {
                continue;
            }

            /** @var \Magento\SalesRule\Model\Rule $rule */
            $rule = $this->_ruleFactory->create();
            $rule->load($ruleId);

            if ($rule->getId()) {
                $rule->loadCouponCode();
                $rule->setTimesUsed($rule->getTimesUsed() + 1);
                $rule->save();

                if ($customerId) {
                    /** @var \Magento\SalesRule\Model\Rule\Customer $ruleCustomer */
                    $ruleCustomer = $this->_ruleCustomerFactory->create();
                    $ruleCustomer->loadByCustomerRule($customerId, $ruleId);

                    if ($ruleCustomer->getId()) {
                        $ruleCustomer->setTimesUsed($ruleCustomer->getTimesUsed() + 1);
                    } else {
                        $ruleCustomer->setCustomerId($customerId)->setRuleId($ruleId)->setTimesUsed(1);
                    }
                    $ruleCustomer->save();
                }
            }
        }

        $this->_coupon->load($order->getCouponCode(), 'code');
        if ($this->_coupon->getId()) {
            $this->_coupon->setTimesUsed($this->_coupon->getTimesUsed() + 1);
            $this->_coupon->save();

            if ($customerId) {
                $this->_couponUsage->updateCustomerCouponTimesUsed($customerId, $this->_coupon->getId());
            }
        }

        return $this;
    }
}

后续操作 #

修复代码后，执行以下命令刷新缓存并重新生成代码：

bin/magento cache:clean
bin/magento cache:flush
bin/magento setup:di:compile

完成后测试下单流程，应该就能解决跳转回购物车的致命错误问题了。

内容的提问来源于stack exchange，提问作者Hassaan