Additional actions when the cart is changed.

[Alvaro Tarela]

I need to do additional actions when the cart is changed.
I need to read the content of the cart and then check a set of conditions. So, I need to know how to put my set of conditions (a function). 
I want to print an error in the cart summary so I need my function to be executed when a product is changed (add or remove) in that screen.
Can I use a module and put my function on it?

This not work for me:

 

public function hookActionCartSave(){
      return $this->checkMyCart();
}

protected function checkMyCart(){
    // My code gos here..

    $this->errors[] = $this->trans(
                $my_error_msg,
                array(),
                'Shop.Notifications.Error'
            );
}

 

 

[Alvaro Tarela]

It doesn't work...

I generate an "alert()" and nothing occurs...

Only when I load the page, but nothing when I change a product quantity in the cart.