Magento 2: How to stop event/observer if another already ran

Question

I have 2 events running if subscribe to newsletter is checked on the checkout page.

1. sales_model_service_quote_submit_success
2. newsletter_subscriber_save_after

Can i prevent event #2 from happening if event #1 has already ran?

Answer 1

This looks like a situation where you might want to store a variable that logs whether that first event has run or not.

If you have an observer for sales_model_service_quote_submit_success, you can make good use of the DataPersistorInterface class to store a temporary session variable that marks whether sales_model_service_quote_submit_success already ran.

So..

class QuoteSubmitSuccessObserver implements ObserverInterface
{
    protected $dataPersistor;

    public function __construct(\Magento\Framework\App\Request\DataPersistorInterface $dataPersistor) {
        $this->dataPersistor = $dataPersistor;
    }

    public function execute(\Magento\Framework\Event\Observer $observer)
    {
        $this->dataPersistor->set('quote_submit_success', true)
    }
}

And

class NewsletterSubscriberSaveObserver implements ObserverInterface
{
    protected $dataPersistor;

    public function __construct(\Magento\Framework\App\Request\DataPersistorInterface $dataPersistor) {
        $this->dataPersistor = $dataPersistor;
    }

    public function execute(\Magento\Framework\Event\Observer $observer)
    {

        if (!$this->dataPersistor->get('quote_submit_success')) {
            … do something here … 
        }
    }
}