Get Categories collection in Helper file give 'Mage' not found error

Question

I am trying to get categories in helper file I am using Mage::() to get categories in my helper file but it is throwing error. Here is the code to my helper file.

<?php
namespace Pulsestorm\HelloWorldMVVM\Helper;
use Magento\Framework\App\Helper\AbstractHelper;

class Data extends AbstractHelper
{

public function getCategoriesDropdown(){
    $categories=Mage::getModel('catalog/category')->getCollection()->addAttributeToSelect('name')->addAttributeToSort('path', 'asc')->addFieldToFilter('is_active', array('eq'=>'1'));
    $first = array();
    $children = array();
    foreach ($categories->getItems() as $cat) {
        if ($cat->getLevel() == 2) {
            $first[$cat->getId()] = $cat;
        } else if ($cat->getParentId()) {
            $children[$cat->getParentId()][] = $cat->getData();
        }
    }
    return array('first' => $first, 'children' => $children);
}
}

Now i am getting this error upon executing my code.

Fatal error: Uncaught Error: Class 'Pulsestorm\HelloWorldMVVM\Helper\Mage' not found in D:\wamp\www\alo_digi_quickstart\app\code\Pulsestorm\HelloWorldMVVM\Helper\Data.php:9 Stack trace: #0

I have to use this result in my phtml file which is here.

  <?php $tree=$this->helper('Pulsestorm\HelloWorldMVVM\Helper\Data')->getCategoriesDropdown();?>
    <script type="text/javascript">
        var children = $H(<?php echo json_encode($tree['children']) ?>);

        function showCat(obj, level) {
            var catId = obj.value;
            level += 1;
            if ($('cat_container_' + level)) {
                $('cat_container_' + level).remove();
            }
            if (children.get(catId)) {
                var options = children.get(catId);
                var html = '<select id="cat_' + catId + '" onchange="showCat(this, ' + level + ')">';
                for (var i = 0; i < options.length; i++) {
                    html += '<option value="' + options[i].entity_id + '">' + options[i].name + '</option>';
                }
                html += '</select>';
                html = '<div id="cat_container_' + level + '">' + html + '</div>';

                $('sub_cat').insert(html);
            }
        }
    </script>
    <select id="first_cat" onchange="showCat(this, 2)">
        <?php foreach ($tree['first'] as $cat): ?>
            <option value="<?php echo $cat->getId() ?>"><?php echo $cat->getName() ?></option>
        <?php endforeach ?>
    </select>
    <div id="sub_cat"></div>

can you help me resolve this problem

Answer 1

The Mage class is no longer available in Magento 2.

Furthermore, Magento 2 would automatically reference the missing class path to the current package where it was declared.

The reason why your getting this

Fatal error: Uncaught Error: Class 'Pulsestorm\HelloWorldMVVM\Helper\Mage' not found 

is because you didn't import the correct path to the Mage class. I can tell it by looking at your "use" statements.

Please follow this link to get the category collection in Magento 2.

Remember not to use Object Manager.

Answer 2

I was trying to make my module from magaplaza hello world tutorial, but something went wrong. I imported code of this module https://github.com/astorm/magento2-hello-world from github and it worked. Whit help of this hello world module i created this functionality as you can see in this picture.

This categories subcategories ajax select drop downs Module. you can check its code here https://github.com/sanaullahAhmad/Magento2_cat_subcat_ajax_select_dropdowns you can access it after installing it in aap/code directory of your magento 2 installation by following URL.. http://www.example.com/hello_mvvm/hello/world