Section Source in Magento2

The section source class is responsible for retrieving data for the section. As a best practice, we recommend that you put your code within the Vendor/ModuleName/CustomerData namespace. Your classes must implement the Magento\Customer\CustomerData\SectionSourceInterface interface.

The public method getSectionData must return an array with data for a private block.

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Customer:etc/sections.xsd">
    <action name="customer/account/editPost">
        <section name="*"/>
    </action>
</config>

Eg:

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Customer:etc/sections.xsd">
    <action name="customer/account/editPost">
        <section name="cart/*"/>
    </action>
</config>

Thank you.