How to rewrite controller in Magento 2

To rewrite controller, you can do it by using preference. It mean that you need to put a rule in your router config using before attribute.

Open Mageplaza/HelloWorld/etc/routes.xml insert the following block of code inside <config> tag rewrite controller in Magento 2

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/ObjectManager/etc/config.xsd">

<router id="standard">
    <route id="mageplaza" frontName="hello">
       <module name="Mageplaza_HelloWorld" before="Magento_Customer" />
    </route>
</router>

</config>

This will completely change controller/action of module Magento_Customer with your controller code, so you should extend rewrite controller and make a change on the function which you want. Also, the controller and action in your module must have same name with rewrite controller/action.

Create Mageplaza/HelloWorld/etc/di.xml and add the code below.

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="Magento\Customer\Controller\Account\Create" type="Mageplaza\HelloWorld\Controller\Account\Create" />
</config>

For example, if you want to rewrite controller: Magento\Customer\Controller\Account\Create.php You have to register a router like above and create a controller:

NameSpace\ModuleName\Controller\Account\Create.php

Content of Create.php file:

namespace Mageplaza\HelloWorld\Controller\Account;

use Magento\Customer\Model\Registration;
use Magento\Customer\Model\Session;
use Magento\Framework\View\Result\PageFactory;
use Magento\Framework\App\Action\Context;

class Create extends \Magento\Customer\Controller\AbstractAccount
{
    /** @var Registration */
    protected $registration;

    /**
     * @var Session
     */
    protected $session;

    /**
     * @var PageFactory
     */
    protected $resultPageFactory;

    /**
     * @param Context $context
     * @param Session $customerSession
     * @param PageFactory $resultPageFactory
     * @param Registration $registration
     */
    public function __construct(
        Context $context,
        Session $customerSession,
        PageFactory $resultPageFactory,
        Registration $registration
    ) {
        $this->session = $customerSession;
        $this->resultPageFactory = $resultPageFactory;
        $this->registration = $registration;
        parent::__construct($context);
    }

    /**
     * Customer register form page
     *
     * @return \Magento\Framework\Controller\Result\Redirect|\Magento\Framework\View\Result\Page
     */
    public function execute()
    {
        if ($this->session->isLoggedIn() || !$this->registration->isAllowed()) {
            /** @var \Magento\Framework\Controller\Result\Redirect $resultRedirect */
            $resultRedirect = $this->resultRedirectFactory->create();
            $resultRedirect->setPath('*/*');
            return $resultRedirect;
        }

        /** @var \Magento\Framework\View\Result\Page $resultPage */
        $resultPage = $this->resultPageFactory->create();
        return $resultPage;
    }
}

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