Inserting a class on before_widget if checkbox is checked

I eventually use the following to be able to do it:

add_filter('dynamic_sidebar_params', function($params) {
global $wp_registered_widgets;
$this_widget_id = $params[0]['widget_id'];
$this_widget = $wp_registered_widgets[$this_widget_id];
$widget_object = $this_widget['callback'][0];
$all_settings = get_option($widget_object->option_name);
$saved_settings = $all_settings[$params[1]['number']];
if ($saved_settings['myclass']) {
    $classe_to_add = 'myclass ';
    $classe_to_add = 'class=" '.$classe_to_add;
    $params[0]['before_widget'] = str_replace('class="',$classe_to_add,$params[0]['before_widget']);
}
return $params;

});