Magento 2 - How to save custom filed data of registration page?

Question

Please see this screenshot,

enter image description here

I try with Install Data

<?php
namespace CP\Customerattribute\Setup;
use Magento\Customer\Setup\CustomerSetupFactory;
use Magento\Customer\Model\Customer;
use Magento\Eav\Model\Entity\Attribute\Set as AttributeSet;
use Magento\Eav\Model\Entity\Attribute\SetFactory as AttributeSetFactory;
use Magento\Framework\Setup\InstallDataInterface;
use Magento\Framework\Setup\ModuleContextInterface;
use Magento\Framework\Setup\ModuleDataSetupInterface;
/**
* Install data
* @codeCoverageIgnore
*/
class InstallData implements InstallDataInterface
{
 /**
 * CustomerSetupFactory
 * @var CustomerSetupFactory
 */
 protected $customerSetupFactory;
 /**
 * $attributeSetFactory
 * @var AttributeSetFactory
 */
 private $attributeSetFactory;
 /**
 * initiate object
 * @param CustomerSetupFactory $customerSetupFactory
 * @param AttributeSetFactory $attributeSetFactory
 */
 public function __construct(
 CustomerSetupFactory $customerSetupFactory,
 AttributeSetFactory $attributeSetFactory
 ) {
 $this->customerSetupFactory = $customerSetupFactory;
 $this->attributeSetFactory = $attributeSetFactory;
 }
 /**
 * install data method
 * @param ModuleDataSetupInterface $setup
 * @param ModuleContextInterface $context
 */
 public function install(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
 {
 /** @var CustomerSetup $customerSetup */
 $customerSetup = $this->customerSetupFactory->create(['setup' => $setup]);
 $customerEntity = $customerSetup->getEavConfig()->getEntityType('customer');
 $attributeSetId = $customerEntity->getDefaultAttributeSetId();
 /** @var $attributeSet AttributeSet */
 $attributeSet = $this->attributeSetFactory->create();
 $attributeGroupId = $attributeSet->getDefaultGroupId($attributeSetId);
 /**
 * customer registration form default field mobile number
 */
 $customerSetup->addAttribute(Customer::ENTITY, 'custom_field', [
 'type' => 'varchar',
 'label' => 'ID Documents',
 'input' => 'text',
 'required' => true,
 'visible' => true,
 'user_defined' => true,
 'sort_order' => 1000,
 'position' => 1000,
 'system' => 0,
 ]);
 //add attribute to attribute set
 $attribute = $customerSetup->getEavConfig()->getAttribute(Customer::ENTITY, 'custom_field')->addData([
 'attribute_set_id' => $attributeSetId,
 'attribute_group_id' => $attributeGroupId,
 'used_in_forms' => ['adminhtml_customer', 'customer_account_create'],
 ]);
 $attribute->save();
 }
}**

• Renga: Check this reference link Create Custom Field in User Registration Page

Answer 1

You can override this controller Magento\Customer\Controller\Account\CreatePost with di.xml

and Below code will help you to save custom attribute value

 <?php
 public function __construct(
 \Magento\Customer\Api\CustomerRepositoryInterface $customerRepository,
 \Magento\Framework\App\Action\Context $context
 )
 { 
 $this->customerRepository = $customerRepository;
 parent::__construct($context);
 }
 public function execute(){
 $customerId = XX;
 $customer = $this->customerRepository->getById($customerId);
 $customer->setCustomAttribute('custom_attribute!','value for attribute');
 try { 
 $customer = $this->customerRepository->save($customer);
 }catch (Exception $e) {
 return $e->getMessage();
 }
 }

So what we did here, in Magento 2 we have to user setCustomAttribute method to save custom customer attribute.

For overriding that controller you may refer to this post https://magento.stackexchange.com/a/154517/49821

Answer 2

Add additional field in a customer account.

Check the reference link Reference Link