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What is the difference between type and virtualType

Jun 15, 2020     5 min read

Virtual types are a way to inject different dependencies into existing classes without affecting other classes.

For example, the Magento\Framework\Session\Storage class takes a namespace argument in its constructor, which defaults to the value 'default', and you could use the type definition to change the namespace to 'core'.

core

The above config would make it so that all instances of Magento\Framework\Session\Storage have a namespace of 'core'. Using a virtual type allows for the equivalent of a sub-class to be created, where only the sub-class has the altered argument values.

In the codebase we see the following two configurations:

<?php

<virtualType name="Magento\Core\Model\Session\Storage" type="Magento\Framework\Session\Storage">
    <arguments>
        <argument name="namespace" xsi:type="string">core</argument>
    </arguments>
</virtualType>

<type name="Magento\Framework\Session\Generic">
    <arguments>
        <argument name="storage" xsi:type="object">Magento\Core\Model\Session\Storage</argument>
    </arguments>
</type>

?>

The first snippet creates a virtual type for Magento\Core\Model\Session\Storage which alters the namespace, and the second inject the virtual type into Magento\Framework\Session\Generic This allows Magento\Framework\Session\Generic to be customized without affecting other classes that also declare a dependency on Magento\Framework\Session\Storage

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