问Symfony Form Builder:如何将字段动态添加到投票

EN

public function buildForm(FormBuilderInterface $builder, array $options)
{
    $builder->add('userAddFlag');

    $builder->add('fields', CollectionType::class, array(
        'entry_type' => FieldType::class,
        'entry_options' => array('label' => false),
        'allow_add' => true,
    ));
}

<ul class="fields" data-prototype=" {{ form_widget(line.fields.vars.prototype)|e('html_attr') }} ">
    <li>
        {% for field in line.fields %}
            <div>
                {% for pollResult in field.pollResults %}
                    <div class="formLabelDiv">{{ field.vars.value.getTranslationName(app.request.getLocale()) }}</div>
                    <div class="formWidgetDiv">{{ form_widget(pollResult) }}</div>
                {% endfor %}
            </div>
        {% endfor %}
    </li>
</ul>

<script>
    var $collectionHolder;

    //setup an "add a Line" Link
    var $addLineButton = $('<button type="button" class="add_line_link">Add a Line</button>');
    var $newLinkLi = $('<li></li>').append($addLineButton);

    jQuery(document).ready(function (){
        //Get the ul that holds the collection of fields
        $collectionHolder = $('ul.fields');

        //add the "add a line" anchor and li to the tags ul
        $collectionHolder.append($newLinkLi);

        //count the current form inputs we have, use that as the new index when inserting a new item
        $collectionHolder.data('index', $collectionHolder.find(':input').length);

        $addLineButton.on('click', function (e){
            addFieldsForm($collectionHolder, $newLinkLi);
        })
    })

    function addFieldsForm($collectionHolder, $newLinkLi){
        //get the data-prototyp
        var prototype = $collectionHolder.data('prototype');

        //get the new index
        var index = $collectionHolder.data('index');

        var newForm = prototype;

        $collectionHolder.data('index', index+1);

        // Display the form in the page in an li, before the "Add a tag" link li
        var $newFormLi = $('<li></li>').append(newForm);
        $newLinkLi.before($newFormLi);

    }
</script>