Add custom post type to category loops

//Add Resource custom post type to default query for category archive
add_filter( 'pre_get_posts', 'add_resource_post_type'  );
function add_resource_post_type( $query ) {
    if ( is_category() ||  !is_admin() && $query->is_category_page ) {
        if(!is_array($query->query_vars['post_type'])) {
          $postTypes = array($query->query_vars['post_type']);
        } else {
          $postTypes = $query->query_vars['post_type'];
        }
        if(!in_array('resources',$postTypes)) {
          if(count($postTypes) == 1 && trim($postTypes[0]) == "") {
            $postTypes[] = 'post';
            $postTypes[] = 'resources';
          } else {
            $postTypes[] = 'resources';
          }
        }

        $query->query_vars['post_type'] = $postTypes;
//         print_r($postTypes);
    }
    return $query;
}