When the magento2.4 order status changes to completed, can I perform an event to process one of my tasks

Question

When the magento2.4 order status changes to completed, can I perform an event to process one of my tasks

Answer 1

As far as I know, there is no such event which observes specific order status complete. Still, you can try with sales_order_state_change_before or sales_order_save_after events.

Solution #1: sales_order_save_after event:

Observer/SalesOrderAfterSave.php

public function execute(\Magento\Framework\Event\Observer $observer)
{
    $order = $observer->getEvent()->getOrder();
    if ($order instanceof \Magento\Framework\Model\AbstractModel) {
       if($order->getState() == 'complete') {
            //Your code here
       }
    }
    return $this;
}

Solution #2: sales_order_state_change_before event:

Observer/SalesOrderStateChangeBefore.php

public function execute(\Magento\Framework\Event\Observer $observer)
{
    $transport = $observer->getEvent()->getTransport();
    if ($transport->getState() == "complete") {
        //Your code here
    }
    return $this;
}

Solution #3 You can try using Plugin also:

etc/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\Sales\Api\OrderRepositoryInterface">
        <plugin name="order_state_plugin"
                type="Company\Module\Model\Plugin\OrderStatePlugin"/>
    </type>
</config>

OrderStatePlugin.php

public function afterSave(
    \Magento\Sales\Api\OrderRepositoryInterface $subject,
    $result
) {
    if($result->getState() == Order::STATE_COMPLETE) {
        ......
    }
    return $result;
}

Let me know if it helped.