自定义窗体小部件Symfony 2但返回控制器中的异常

Question

我正在尝试使用{{form_widget（form）}}在symfony2中自定义我的表单 所以我的buildForm是这样的：

$builder
    ->add('Status', 'choice', array(
        'choices'   => array('Required' => 'Required', 'Free' => 'Free', 'OnArrival' => 'OnArrival', 'Refused' => 'Refused'),
        'required'  => true,
        'label'  => 'Visa required?'
         ))
    ->add('Length', null, array('required'  => false, 'label'  => 'Max Stay'))
    ->add('Description', 'textarea',array('required'  => false, 'label'  => 'Additional information'));

我的twig html：

{% block choice_widget %}
<div class="row"> 
    <div class="col-md-8 "> 
        <select  class="selectpicker " data-style="btn-primary">
        {% spaceless %}
            {% for  choice in choices %}
                <option value="{{ choice.value }}">{{ choice.value }}</option>
            {% endfor %}
        {% endspaceless %}
        </select>
    </div>
</div>
{% endblock %}


{% block text_widget %}
    <div class="row">
        <div class="col-md-8 "> 
            <input id="id_max" type="text" placeholder=" x Month(s)" class="form-control">
        </div>
    </div> 
{% endblock %}


{% block textarea_widget %}
    <textarea id="id_desc" type="" placeholder="" class="form-control"></textarea>
{% endblock %} 

它很好地展示了应用的新样式，但是当我执行我的表单时，它返回一个异常，并说值为null，即：Status=null , length=null, description=null PS：当我检索自定义HTML时，它运作良好

编辑：添加控制器部分

   /**
     * Creates a new TravelInfoCorrection entity.
     *
     * @Route("/correct/create", name="correct_create")
     * @Method("POST")
     * @Template("TechyVisaBundle:edit:new.html.twig")
     */
    public function createAction(Request $request)
    {
        $entity  = new TravelInfoCorrection();
        $form = $this->createForm(new TravelInfoCorrectionType(), $entity);
        $form->bind($request);

        $entity->setCreatedAt(new \DateTime('now'));
        $entity->setProcessedFlag('Pending');


        if (! $form->isValid()) throw new \Exception('Form not valid');

        $em = $this->getDoctrine()->getManager();
        $orientity = $em->getRepository('TechyVisaBundle:TravelInfo')
        ->findOneBy(array( 'TravFrom' => $entity->getTravFrom(), 'TravTo' => $entity->getTravTo() ));
        $isdiff = false;
        $isdiff = $isdiff || ($entity->getStatus() != $orientity->getStatus());
        $isdiff = $isdiff || ($entity->getLength() != $orientity->getLength());
        $isdiff = $isdiff || ($entity->getDescription() != $orientity->getDescription());

        if ($isdiff){
            $em->persist($entity);
            $em->flush();
        }

        return $this->redirect($this->generateUrl('thanks'));
    }

和来电者html：

{% form_theme form 'TechyVisaBundle:Form:fields.html.twig' %}

{% block content %}
<br/>
<div id="sign_up1">
    <div class="container">
        <h2>Edit information {{ from.getName }} to {{ to.getName }} travelling information</h2>

        <b style="color: red;">Please verify your informations <a target="_blank" rel="nofollow" href="http://www.gulfair.com/English/info/prepare/Pages/VisaInformation.aspx">here</a> before posting it</b>
        <br/>

        <form action="{{ path('correct_create') }}"  method="post" {{ form_enctype(form) }} class="form-inline">

        {{ form_widget(form) }}

            <button type="submit">Submit correction</button>
        </form>



    </div>
</div>
{% endblock %}