code: public function switcher($options = [], $flags = null)
      {
          parent::checkbox($options, false);
          if ($flags === null) {
              $label = Html::encode($this->model->getAttributeLabel(Html::getAttributeName($this->attribute)));
              $labelParts = explode(',', $label);
              $flags = count($labelParts) >= 2 ? $labelParts : null;
          }
          if ($flags) {
              Html::removeCssClass($this->options, 'input-field');
              Html::addCssClass($this->options, 'switch');
              $labelContent = $flags[0] . $this->parts['{input}'] . Html::tag('span', '', ['class' => 'lever']) . $flags[1];
              $this->parts['{input}'] = Html::label($labelContent, Html::getInputId($this->model, $this->attribute));
          }
          return $this;
      }
docs: Renders switcher
  @see http://materializecss.com/forms.html#switches
  @param array $options
  @param array $flags
  @return $this