abstract class FormHandler extends Nette\Object
{
    public function attach(Form $form)
    {
        $that = $this;
        if (method_exists($this, 'handleSuccess')) {
            $form->onSuccess[] = function (Form $form) use ($that) {
                if (!$form->isValid()) return;
                $that->handleSuccess($form->getValues());
            };
        }
        if (method_exists($this, 'handleError')) {
            $form->onError[] = function (Form $form) use ($that) {
                $that->handleError($form->getValues());
            };
        }
    }

    public function attachButton(SubmitButton $button)
    {
        $that = $this;
        if (method_exists($this, 'handleClick')) {
            $button->onClick[] = function (SubmitButton $button) use ($that) {
                $that->handleClick($form->getValues());
            };
        }
        if (method_exists($this, 'handleError')) {
            $button->onInvalidClick[] = function (SubmitButton $button) use ($that) {
                $that->handleError($form->getValues());
            };
        }
    }
}

class RegistrationHandler extends FormHandler
{
    public $onFoo = array();
    public $onBar = array();

    public function handleSuccess($values) { ... }
}

$form = new Form;
$handler = new RegistrationHandler();
$handler->attach($form);
$handler->attachButton($form->addSubmit('send', "Odeslat"));