Whats the best way to override a block class in magento2

Question

1) Use preference in di.xml and add new methods or do changes

2) Or create a new class which extends the actual class and attach the new class to your phtml.

Lets suppose you want to extend Magento\Catalog\Block\Product\Listproduct then you create a class like Vendor\Module\Block\Product\Listproduct and change here

<block class="Vendor\Module\Block\Product\Listproduct" name="category.products.list" as="product_list" template="Magento_Catalog::product/list.phtml">

Answer 1

Rather than extend block use Plugin

There is three type of plugin

• Before plugin

• After plugin

• Around plugin

For more info please refer link

Answer 2

The best way to override a block would be a plugin, but note that a plugin can not be used on following:

1. Final methods
2. List item
3. Non-public methods
4. Class methods (such as static methods)
5. __construct
6. Virtual types
7. Objects that are instantiated before Magento\Framework\Interception is bootstrapped.

Reference - https://devdocs.magento.com/guides/v2.3/extension-dev-guide/plugins.html