Magento 2 :- how to get the subcategories from main category url

Question

I want to get the subcategories of a main category using main category url.

I tried in this way in a function in my block.

$category = $this->_categoryFactory->create()->getCollection()
    ->addAttributeToFilter('url_key',$url_key);

but i cannot get any thing.

Answer 1

Get Category

$categoryCollection = $this->_categoryFactory->create()->getCollection()      
                    ->addAttributeToFilter('url_key',$url_key)->getFirstItem(); 

$childs = $categoryCollection->getChildrenCategories();
foreach ($childs as  $child) {
   echo $child->getUrlKey();
}