Symfony Twig将月份设置为表格上的选定值

I followed this post, to set up a month year widget for credit card expiry date:

How to display a month-year dropdown in Symfony2

Now I am trying to set the fields to the values selected during form submission. How do I do this?

My form Type:

$builder->add('card_expiration_date', 'date', array(
            'mapped' => false,
            'widget' => 'choice',
            'empty_value' => array('year' => 'Year', 'month' => 'Month', 'day' => 'Day'),
            'format' => 'dd-MM-yyyy',
            'input' => 'string',
            'data' => date('Y-m-d'),
            'years' => range(date('Y'), date('Y') + 10)
        ));

Some of the things I've been trying to do are:

Trial 1:

{{ form_widget(form.card_expiration_date.month, {'value': ccMonth}) }}
{{ form_widget(form.card_expiration_date.year, {'value': ccYear}) }}

This sets the values correctly but the issue with this is that it still renders out the form.card_expiration_date

Trial 2:

{%  if ccMonth == '' and ccYear == ''  %}
    {{ form_widget(form.card_expiration_date, {'date_pattern': '<span style="display: none;">{{ day }}</span> {{ month }} <span class="delim">&#47;</span> {{ year }}'}) }}
{% else %}
    {{ form_widget(form.card_expiration_date, {'date_pattern': '<span style="display: none;">{{ day }}</span> {{ month }} <span class="delim">&#47;</span> {{ year }}', 'value':  cmonth~'/'~cyear  }) }}
{% endif %}

I am pretty sure there's a better way to set the value on my Trial 2. That just doesn't look right. Any help will be appreciated.

EDIT

Trial 3:

{%  if cmonth == '' and cyear == ''  %}
    {{ form_widget(form.card_expiration_date, {'date_pattern': '<span style="display: none;">{{ day }}</span> {{ month }} <span class="delim">&#47;</span> {{ year }}'}) }}
{% else %}
    {{ form_widget(form.card_expiration_date, {'date_pattern': '<span style="display: none;">{{ day }}</span> {{ month }} <span class="delim">&#47;</span> {{ year }}'}) }}
    {{ form_widget(form.card_expiration_date.month, {'value': cmonth}) }}
    {{ form_widget(form.card_expiration_date.year, {'value': cyear}) }}
{% endif %}

EDIT2

{% set ccMonth = cardInfo.card.expdate|slice(2, 2) %}
{% set cmonth = (cardInfo.card)? ((ccMonth starts with '0')? ccMonth|slice(1, 1) : ccMonth) : '' %}
{% set cyear = (cardInfo.card)? '20'~cardInfo.card.expdate|slice(0, 2) : '' %}

<div class="col-lg-8">
    {%  if cmonth == '' and cyear == ''  %}
        {{ form_widget(form.card_expiration_date, {'date_pattern': '<span style="display: none;">{{ day }}</span> {{ month }} <span class="delim">&#47;</span> {{ year }}'}) }}
    {% else %}
        {{ form_widget(form.card_expiration_date, {'date_pattern': '<span style="display: none;">{{ day }}</span> {{ month }} <span class="delim">&#47;</span> {{ year }}'}) }}
        {{ form_widget(form.card_expiration_date.month, {'value': cmonth}) }}
        {{ form_widget(form.card_expiration_date.year, {'value': cyear}) }}
    {% endif %}
    {{ form_errors(form.card_expiration_date) }}
</div>

EDIT3

Here's what I did. Not sure if it's the right way, but seems to work.

Controller:

$form = $this->createForm(new BillingType($em, $ccInfo), $billing, array(
        'action' => $this->generateUrl('save_billing', array('id' => $id)),
        'method' => 'POST'
    ));

BillingType:

function __construct(EntityManager $em, $ccInfo)
{
    $this->em = $em;
    $this->ccInfo = $ccInfo;
}

public function buildForm(FormBuilderInterface $builder, array $options)
{
    $date = date('Y-m-d');

    if( ! is_null($this->ccInfo['card']))
    {
        if (substr($this->ccInfo['card']['expdate'], -2, 1) == '0')
        {
            $ccMonth = substr($this->ccInfo['card']['expdate'], -1, 1);
        }
        else
        {
            $ccMonth = substr($this->ccInfo['card']['expdate'], -2, 2);
        }
        $ccYear = '20'.substr($this->ccInfo['card']['expdate'], 0, 2);

        $date = date('Y-m-d', strtotime($ccYear.'-'.$ccMonth.'-01'));
    }

$builder->add('card_expiration_date', 'date', array(
            'mapped' => false,
            'widget' => 'choice',
            'empty_value' => array('year' => 'Year', 'month' => 'Month', 'day' => 'Day'),
            'format' => 'dd-MM-yyyy',
            'input' => 'string',
            'data' => $date,
            'years' => range(date('Y'), date('Y') + 10)
        ));
}

Neither. You should set the data of the underlying object (or array). The form_widget view helper will already render the value if one is present. If you're in a controller context, there's already a method for doing this

$form->handleRequest($this->getRequest());

This will bind the request data to the form's data object. I can help you iron out your specific implementation if you want to share more details.