public function addFinish($callback)
    {
        if (count($this->steps) == $this->currentStep + 1) {
            $this->buttonFinish->link($this->stepCallback->getURL(count($this->steps)));
        } elseif ($this->currentStep == count($this->steps)) {
            $this->buttonPrev->destroy();
            $this->buttonNext->addClass('disabled')->set('Completed');
            $this->buttonFinish->destroy();

            $this->app->catch_runaway_callbacks = false;
            call_user_func($callback, $this);
        } else {
            $this->buttonFinish->destroy();
        }
    }