How to Override the block in magento2.3

Question

I want override the block file. I had given the details of the original file path and my overridden file.

My overridden file

app\code\Vendor\Module\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">
    <preference for="Sm\MegaMenu\Block\MegaMenu\View" type="Sm\MageMenuCutomize\Block\MageMenu\View" />
</config>

app\code\Vendor\Module\etc\module.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
    <module name="Sm_MageMenuCutomize" setup_version="1.0.0" schema_version="1.0.0">
    </module>
</config>

app\code\Vendor\duplicate\Block\Menu\View.php

<?php
namespace Vendor\duplicate\Block\Menu;           
class View extends Template
{
    /* My Code*/
}

My Original File

app\code\Vendor\original\Block\Menu\View.php

<?php
    namespace Vendor\original\Block\Menu;           
    class View extends Template
    {
        /* My Code*/
    }

I got the empty page after this processed is finished. What is the best way to over ride this.

Thanks in advance.

Answer 1

Following step need to follow

create app/code/Vendor/ModuleName/registration.php

\Magento\Framework\Component\ComponentRegistrar::register(
            \Magento\Framework\Component\ComponentRegistrar::MODULE,
            'Vendor_ModuleName',
            __DIR__
        );

create app/code/Vendor/ModuleName/etc/module.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
        <module name="Vendor_ModuleName" setup_version="1.0.0" />
    </config>

create app/code/Vendor/ModuleName/etc/di.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="ThirdPartyVendor\ThirdpartyModule\Block\File.php" type="Vendor\ModuleName\Block\File.php"/>
</config>

create app/code/Vendor/ModuleName/Block/File.php

namespace Vendor\ModuleName\Block;
use ThirdPartyVendor\ThirdpartyModule\Block\File as ThirdPartyFile;

class File extends ThirdPartyFile
{
...........
...........
}

And Finally Run Below Commands:

 php bin/magento setup:di:compile
 php bin/magento c:f

Answer 2

Block overriding is a bad development practice. You have to create custom layout for needed page and just replace block class where needed. Example:

<referenceBlock name="needed.block" class="Sm\MageMenuCutomize\Block\MageMenu\View">

It's obvious that your custom block have to extend original block.