Magento 2: Add class to pre existing xml container

Question

How do you add a class to a pre existing xml block?

Example:

<container name="alert.urls" as="alert_urls" label="Alert Urls" after="product.price.tier"/>
            <block class="Magento\Catalog\Block\Product\View" name="product.info" template="product/view/form.phtml" after="alert.urls">
</container>

Answer 1

Recently I've had the need for the exact same function. I decided to look at the core XML files, and found the following code to work:

<referenceBlock name="product.info" htmlClass="yourClassName canUseMutipleNames" />

I found the above code in the core file at this location:

/vendor/magento/module-theme/view/frontend/layout/default.xml

You can use this file as a reference and find some other useful tags like htmlTag :)

Answer 2

I have found some code in Magento XML core file

Please Try this code:

container name = "container_name" label="form" htmlTag="div" htmlClass="old-class" after='-'

Answer 3

Since Magento 2.3.2 you need to use arguments to referenceBlock/referenceContainer, for container/block use htmlClass

<arguments>
    <argument name="css_class" xsi:type="string">header links</argument> 
</arguments>