I need to filter the customers Array in

“Admin Panel -> Customers -> All Customers”

BEFORE the list is rendered, by an private attribute. The attribute is already exist.

I have 3 different admin user, those are have access to just their customers. All Customers have an attribute called “manager_id”. On the php side, i need to check which user is loged in and filter customers by “manager_id” and display those.

Solution:-

We need to display the customer data in the customer grid. Grid itself is an UI component and is stored in the Magento file /vendor/magento/module-customer/view/adminhtml/ui_component/customer_listing.xml.

There, it is configured to using the collection Magento\Customer\Ui\Component\DataProvider via data source named customer_listing_data_source.

To customize it as per your requirement, you may follow steps below :

Assume you are using a custom extension named “Thecoachsmb_MyModule“.

Also, Assume the customer attribute you mention (i.e “manager_id“) is contain admin user_id or user_mail of an admin user

Step 1: 

Create a di.xml under app/code/Thecoachsmb/MyModule/etc/di.xml

File: /app/code/Thecoachsmb/MyModule/etc/di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
<type name="Magento\Framework\View\Element\UiComponent\DataProvider\CollectionFactory">
    <arguments>
        <argument name="collections" xsi:type="array">
            <item name="customer_listing_data_source" xsi:type="string">Thecoachsmb\MyModule\Model\ResourceModel\Customer\Grid\Collection</item>
        </argument>
    </arguments>
</type>
</config>

Step 2: 

Create the class Collection.php under /app/code/Thecoachsmb/MyModule/Model/ResourceModel/Customer/Grid/

File : /app/code/Thecoachsmb/MyModule/Model/ResourceModel/Customer/Grid/Collection.php

<?php
    namespace Thecoachsmb\MyModule\Model\ResourceModel\Customer\Grid;
    use Magento\Customer\Model\ResourceModel\Grid\Collection as CusCollection;
    use Magento\Framework\Data\Collection\Db\FetchStrategyInterface as FetchStrategy;
    use Magento\Framework\Data\Collection\EntityFactoryInterface as EntityFactory;
    use Magento\Framework\Locale\ResolverInterface;
    use Magento\Framework\Event\ManagerInterface as EventManager;
    use Psr\Log\LoggerInterface as Logger;


    class Collection extends CusCollection{
        protected $_authSession;
        protected $logger;
        private $localeResolver;

        public function __construct(
           EntityFactory $entityFactory,
           Logger $logger,
           FetchStrategy $fetchStrategy,
           EventManager $eventManager,
           ResolverInterface $localeResolver,
           \Magento\Backend\Model\Auth\Session $authSession)
        {        
           $this->_authSession = $authSession;
           $this->logger = $logger;
           $this->localeResolver = $localeResolver;
           parent::__construct($entityFactory, $logger, $fetchStrategy, $eventManager);
        }

        protected function _renderFiltersBefore() {
            $user = $this->_authSession->getUser();
            $loggedUserId =  $user->getId();
            $this->getSelect()->where('refer='.$loggedUserId);
            parent::_renderFiltersBefore();
        }
    }
?>

Step 3: 

we need to instruct the grid to display our new column. create file customer_listing.xml under app/code/Thecoachsmb/MyModule/view/adminhtml/ui_component/

File : app/code/Thecoachsmb/MyModule/view/adminhtml/ui_component/customer_listing.xml

<?xml version="1.0" encoding="UTF-8"?>
<listing xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd">
 <columns name="customer_columns">
 <column name="manager_id">
 <argument name="data" xsi:type="array">
 <item name="config" xsi:type="array">
 <item name="filter" xsi:type="string">text</item>
 <item name="label" xsi:type="string" translate="true">Manager Id</item>
 </item>
 </argument>
 </column>
 </columns>
</listing>

step 4: Run Following commands

php bin/magento indexer:reindex

php bin/magento cache:flush