Nette\Forms\Form::beforeRender PHP Method

    protected function beforeRender()
    {
    }

 protected function beforeRender()
 {
     parent::beforeRender();
     $key = ($this->isMethod('post') ? '_' : '') . Presenter::SIGNAL_KEY;
     if (!isset($this[$key])) {
         $do = $this->lookupPath(Presenter::class) . self::NAME_SEPARATOR . 'submit';
         $this[$key] = (new Nette\Forms\Controls\HiddenField($do))->setOmitted()->setHtmlId(FALSE);
     }
 }