Model Admin Search Form

ProductCatalogAdmin.php

<?php

namespace Company\ProductCatalog\Admin;

use Company\ProductCatalog\Model\Product;
use Company\ProductCatalog\Model\Vendor;
use Company\ProductCatalog\Model\ProductTag;
use Company\ProductCatalog\Model\ProductIndustry;
use Company\ProductCatalog\Model\Manufacturer;

use SilverStripe\Forms\CheckboxField;
use SilverStripe\Forms\GridField\GridFieldFilterHeader;

use SilverStripe\Admin\ModelAdmin;

/**
 * Description
 *
 * @package silverstripe
 * @subpackage mysite
 */
class Admin extends ModelAdmin
{
    /**
     * Managed data objects for CMS
     * @var array
     */
    private static $managed_models = [
        Product::class,
        Vendor::class,
        Manufacturer::class,
        ProductTag::class,
        ProductIndustry::class,
    ];

    /**
     * URL Path for CMS
     * @var string
     */
    private static $url_segment = 'product-catalog';

    /**
     * Menu title for Left and Main CMS
     * @var string
     */
    private static $menu_title = 'Product Catalog';

    public function getEditForm($id = null, $fields = null)
    {
        $form = parent::getEditForm($id, $fields);
        $modelClass = $this->modelClass;

        if($modelClass == ProductIndustry::class) {
            // $gridFieldName is generated from the ModelClass, eg if the Class 'Product'
            // is managed by this ModelAdmin, the GridField for it will also be named 'Product'
            $gridFieldName = $this->sanitiseClassName($modelClass);
            $gridField = $form->Fields()->fieldByName($gridFieldName);
            $filterHeader = $gridField->getConfig()
            ->getComponentByType(GridFieldFilterHeader::class);

            // Add more search fields
            $context = $filterHeader->getSearchContext($gridField);
            $context->getFields()->push(new CheckboxField('ParentIndustry', 'Only Parent Industries'));
            $context->getFields()->push(new CheckboxField('ChildIndustry', 'Only Child Industries'));
        }

        return $form;
    }

    public function getList()
    {
        // print("Model Class -> ".$this->modelClass);
        $list = parent::getList();

        $filterParam = $this->getRequest()->requestVar('filter');

        if($this->modelClass == ProductIndustry::class && $filterParam && isset($filterParam["Company-ProductCatalog-Model-ProductIndustry"])) {
            $filterNamespaceParam = $filterParam["Company-ProductCatalog-Model-ProductIndustry"];
            if (isset($filterNamespaceParam["ParentIndustry"]) && $filterNamespaceParam["ParentIndustry"]) {
                // print("ParentIndustry is set to -> ".$parentIndustryParam);
                $list = $list->exclude('ParentIndustryID:not', '0');
            } else if (isset($filterNamespaceParam["ChildIndustry"]) && $filterNamespaceParam["ChildIndustry"]) {
                // print("ChildIndustry is set to -> ".$childIndustryParams);
                $list = $list->exclude('ParentIndustryID', '0');
            }
        }

        return $list;
    }

}