RainLab\Blog\Models\Category::getCategoryPageUrl PHP Method

    protected static function getCategoryPageUrl($pageCode, $category, $theme)
    {
        $page = CmsPage::loadCached($theme, $pageCode);
        if (!$page) {
            return;
        }
        $properties = $page->getComponentProperties('blogPosts');
        if (!isset($properties['categoryFilter'])) {
            return;
        }
        /*
         * Extract the routing parameter name from the category filter
         * eg: {{ :someRouteParam }}
         */
        if (!preg_match('/^\\{\\{([^\\}]+)\\}\\}$/', $properties['categoryFilter'], $matches)) {
            return;
        }
        $paramName = substr(trim($matches[1]), 1);
        $url = CmsPage::url($page->getBaseFileName(), [$paramName => $category->slug]);
        return $url;
    }