public function display()
    {
        if (!$this->isVisible()) {
            return;
        }

        parent::display();

        if (count($this->replicators) < $this->number) {
            $diff = $this->number - count($this->replicators);
            $next_replicator =
                count($this->replicators) === 0
                    ? 0
                    : end($this->replicators) + 1;

            for ($i = $next_replicator; $i < $diff + $next_replicator; $i++) {
                $this->replicators[] = $i;
            }
        }

        // add replicator ids to the form as a hidden field
        $this->getForm()->addHiddenField(
            $this->getId() . '_replicators',
            implode(',', $this->replicators)
        );

        $this->displayInputRows();
        $this->displayEnterAnotherRow();
    }