配置在OpenCart扩展中的位置

Question

I am currently developing OpenCart extensions. I am looking through existing extensions to understand the architecture (and familiarizing MVC/PHPOO concepts).

Frequently, this line of code comes up:

$seller_email = $this->config->get('service_seller_email');

My interpretation based on reading this thread:

I understand that this is a variable assignment, where it's accessing a model (?) called config to retrieve a string called service_seller_email from the admin settings portal. However, I have tried navigating through the various MVC folders within OpenCart, and I could not find a specific config.php. Could you please correct my interpretation if it's wrong?

EDIT: To add to the confusion, the article I linked specifies that you need to load a config in a controller before using it, like $this->language->load('product/search');, but I cannot find a line such as $this->config->load('...'); or the like.

Answer 1

Your interpretation is incorrect. The config class is not considered as model (despite it is accessing DB directly) but as a system library class - that's why you can find it under system/library/ folder.

OpenCart has it's implementation of service locator (registry) which is used to to store the config object so that you can access it directly from anywhere (inside of OpenCart of course).

It is loaded in both index.php files (in root and under admin/) like this:

$config = new Config();
$registry->set('config', $config);

This $registry is our service locator and it is passed over to any controller in it's __construct() method. Each controller has also a magic method __get() which is responsible for retrieving objects from this $registry - take a look at abstract Controller class at system/engine/controller.php which each controller extends (and should extend).

That's why you can freely call directly

$this->config->get('some_config_key');

The first part, $this->config will fall into the __get() method passing over the 'config' value as a $key which in turn is passed over to next call

return $this->registry->get($key);

And since the config object is registered under 'config' key in our service locator, it is retrieved and returned so that we could call get('some_config_key') on it.

Now the some_config_key key is stored in DB in setting table and the config object tries to find it and get it's value (you can take a look at how this works in system/library/config.php).

Hopefully this clarifies your confusion.