what does $this->_coreRegistry->registry('current_category') return in magento 2?

Question

what does $this->_coreRegistry->registry('current_category') return in magento 2 ?

Answer 1

$this->_coreRegistry is an instance of \Magento\Framework\Registry (vendor/magento/framework/Registry.php)

register method in \Magento\Framework\Registry register a new variable and store it in Registry.

registry method in \Magento\Framework\Registry returns the value of a registered variable in Registry otherwise, it returns null.

You can search in the Magento core directory (vendor/magento) with the search term: ->register('current_category' to know which value is set to current_category.

Finally, you can see $this->_coreRegistry->registry('current_category') return an instance of \Magento\Catalog\Model\Category or null.

So, if you visit a page that contains code register current_category:

$this->_coreRegistry->register('current_category', $category);

you can get current_category from Registry:

$this->_coreRegistry->registry('current_category')