How to Create Customer Attribute in Magento 2

<?php

namespace Mageants\Blog\Setup;

use Magento\Eav\Model\Config;

use Magento\Eav\Setup\EavSetup;

use Magento\Eav\Setup\EavSetupFactory;

use Magento\Framework\Setup\InstallDataInterface;

use Magento\Framework\Setup\ModuleContextInterface;

use Magento\Framework\Setup\ModuleDataSetupInterface;

class InstallData implements InstallDataInterface

{

 private $eavSetupFactory;

 public function __construct(

EavSetupFactory $eavSetupFactory,

Config $eavConfig

 ) {

$this->eavSetupFactory = $eavSetupFactory;

$this->eavConfig = $eavConfig;

 }

 public function install(ModuleDataSetupInterface $setup, ModuleContextInterface $context)

 {

$eavSetup = $this->eavSetupFactory->create(['setup' => $setup]);

$eavSetup->addAttribute(

\Magento\Catalog\Model\Customer::ENTITY,

'my_custom_attribute',

[

 'label' => 'My Custom Atrribute',

 'system' => 0,

 'position' => 700,

 'sort_order' => 700,

 'visible' => true,

 'note' => '',

 'type' => 'varchar',

 'input' => 'text',

]);

$this->getEavConfig()->getAttribute('customer', 'my_custom_attribute')->setData('is_user_defined', 1)->setData('is_required', 0)->setData('default_value', '')->setData('used_in_forms', ['adminhtml_customer', 'checkout_register', 'customer_account_create', 'customer_account_edit', 'adminhtml_checkout'])->save();

 }

 public function getEavConfig() {

return $this->eavConfig;

 }

}

<?php

namespace Mageants\Blog\Controller\Index;

class Index extends \Magento\Framework\App\Action\Action

{

 public function __construct(

\Magento\Customer\Model\Customer $customer,

\Magento\Customer\Model\ResourceModel\CustomerFactory $customerFactory,

\Magento\Framework\App\Action\Context $context

 ) {

$this->customer = $customer;

$this->customerFactory = $customerFactory;

return parent::__construct($context);

 }

 public function execute()

 {

$customerId = "1"; // set any cusromer id

$customer = $this->customer->load($customerId);

$data = "new customer value"; // set any value

$customerData = $customer->getDataModel();

$customerData->setCustomAttribute('my_custom_attribute',$data);

$customer->updateData($customerData);

$customerResource = $this->customerFactory->create();

$customerResource->saveAttribute($customer, 'my_custom_attribute');

 }

}

<?php

namespace Mageants\Blog\Controller\Index;

class Index extends \Magento\Framework\App\Action\Action

{

 public function __construct(

\Magento\Customer\Api\CustomerRepositoryInterface $customerRepositoryInterface,

\Magento\Framework\App\Action\Context $context

 ) {

$this->customerRepositoryInterface = $customerRepositoryInterface;

return parent::__construct($context);

 }

 public function execute()

 {

$customer =$this->customerRepositoryInterface->getById(1); // Pass any Customer Id whose custom customer atribute value you want to fetch

print_r($customer->getCustomAttribute('my_custom_attribute')->getValue());

 }

}