How to access my custom model located in catalog from system cart library in opencart 2.3

Question

I am adding this code via modification into system cart library to access my custom model located in catalog/model/extension/folder_name/file_name:

public function __construct($registry) {
global $loader;
$loader->model('extension/folder_name/file_name');
$this->model = $registry->get('model_extension_folder_name_file_name');
}

But it says: Fatal error: Uncaught Error: Call to a member function model() on null in opencart 2.3.0.2

While this code is fine when I work on opencart 2.2.0.0.

Please help...

Answer 1

you got the idea right, just a syntax error.

In OpenCart in a controller file the loader is accessed via $this->load->model()

But in system/library/cart/cart.php your code should look like this

public function __construct($registry) {
    $registry->get('load')->model('extension/folder_name/file_name');
    $this->model = $registry->get('model_extension_folder_name_file_name');
}

This is because you are accessing directly in system/library/cart/cart.php, where you have access to the $registry from the construct but no __get() and __set() functions like the controllers and models have.

The cool thing is, the $this->load->model method actually checks where the cart is being called (is it from catalog folder or admin folder) and loads accordingly.

You can be safe to load a model in cart.php because it is only called in catalog folder, but be careful adding such code to system/library/request.php which is loaded both in catalog and admin. this will creat errors.