Calling Controller action after running code

Question

I am creating a custom form essentially from scratch. The form will be an alternative UI for a product page, which when submitted, does the same thing as the normal add to cart.

I'd like to borrow from the checkout/cart/add controller without copying or rewriting the code, but before I submit I need to run own custom function (to create a file).

Is there any way I can achieve this? Eg, is there an event for an Observer I can use or is it possible to have two Controllers execute one after the other?

Answer 1

The answer was pretty obvious, not sure why I didn't think of this originally. Simply extend the controller and return parent::execute().

namespace Vendor\Module\Controller\Custom;

use Magento\Checkout\Controller\Cart\Add as AddToCart;

class Add extends AddToCart {

    public function execute()
    {

        $this->dothing();

        return parent::execute();

    }
    public function dothing()
    {
        // custom code
    }
}

As a bonus I also learned recently that the Action class has predispatch and post dispatch events that can be hooked into with an Observer, allowing you to run code before or after a controller has fired.

//from Magento\Framework\App\Action\Action
$this->_eventManager->dispatch('controller_action_predispatch', 
$eventParameters);
    $this->_eventManager->dispatch('controller_action_predispatch_' . 
$request->getRouteName(), $eventParameters);
    $this->_eventManager->dispatch(
        'controller_action_predispatch_' . $request->getFullActionName(),
        $eventParameters
    );