Overwrite the Block file and .phtml files

[swamy chaluvadi]

I would like to overwrite the the Block files and .phtml files of the magento modules.Here is example
-Magento Newsletter Module

I want to extended the Block file '\Magento\Newsletter\Block\Subscribe' to the custom Module as mentioned in the below code
<?php
namespace Sample\Test\Block;

class Customsubscribe extends \Magento\Newsletter\Block\Subscribe
{

/**
 * Retrieve form action url and set "secure" param to avoid confirm
 * message when we submit form from secure page to unsecure
 *
 * @return string
 */
public function getFormActionUrl()
{
    return $this->getUrl('newsletter/subscriber/new1231', ['_secure' => true]);
}

}
?>

Add tried to override the subscriber.phtml for Magento newsletter Module to My sample Module 'Test'

In the custom modules folder i add the below code

app\code\Sample\Test\view\frontend\layout\default.xml

    <!--remove name ='form.subscribe'/-->
    <referenceContainer name="footer">
        <block class="Training\Test\Block\Customsubscribe" name="form.subscribe" as="subscribe" before="-" template="subscribe.phtml"/>
    </referenceContainer>
</body>

After Doing that i run the CLI : php bin/magento setup:upgrade, but still the file is loading from the Magento_Newsletter Module .

Can any one please help on the this issues.

[Dmitry_Fedyuk]

One of your errors is you have specified a wrong namespace: you use Sample\Test\Block in the class declaration but Training\Test\Block is the layout default.xml file.

[swamy chaluvadi]

Hi Dmitry_Fedyuk,

I have done correction and tried ,but is not working:

<referenceContainer name="footer">
        <block class="Sample\Test\Block\Customsubscribe" name="form.subscribe" as="subscribe" before="-" template="subscribe.phtml"/>
    </referenceContainer>

[Nguyen Thanh Do]

I think you need to remove block 'form.subscribe' and then redeclare it.

<referenceBlock  name="form.subscribe" remove="true"></referenceBlock>
    <referenceContainer name="footer">
        <block class="Training\Test\Block\Customsubscribe" name="form.subscribe" as="subscribe" before="-" template="subscribe.phtml"/>
    </referenceContainer>
</body>