Build extension

Di.xml file

Areas and application entry points

• Magento loads the configuration in the following stages:

  1. Initial (app/etc/di.xml)
  2. Global (/etc/di.xml)
  3. Area-specific (/etc//di.xml)

Abstraction-implementation mappings

<!--  File: app/etc/di.xml -->
<config>
    <preference for="Magento\Core\Model\UrlInterface" type="Magento\Core\Model\Url" />
</config>

- Classes has relation:

Magento\Framework\ObjectManager\ObjectManager.php
Magento\Framework\ObjectManager\Config.php

- Process: Magento read all file di.xml, save info about Preference in all file di.xml to ObjectManager\Config::_preferences and ObjectManager\Config::_cache.

When call \Magento\Framework\ObjectManagerInterface::create($type), Magento call

public function create($type, array $arguments = [])
{
    return $this->_factory->create($this->_config->getPreference($type), $arguments);
}

Config get preference for once type, then init and return object with construct of preference.

Virtual types