Symfony2-树枝：HTML <optgroup> 标签

Question

I need to create a select with Tag.

this is my code to fill the select

        ->add('city', 'entity', array(
            'empty_value' => 'Choisissez une option',
            'class' => 'FrontBundle:City',
            'query_builder' => function(EntityRepository $er) {
                return $er->createQueryBuilder('c')
                    ->orderBy('c.city', 'ASC');
            },
        ))

And this is my code in html.twig

                    <div class="form-group">
                        {{ form_label(form.city, 'Ville') }}
                        <div class="col-sm-8">
                            {{ form_widget(form.city) }}
                        </div>
                    </div>

Here is the result I want to get:

<select>
  <optgroup label="Région 1">
     <option value="ville 1">Ville 1</option>
     <option value="ville 2">Ville 2</option>
  </optgroup>
  <optgroup label="Région 2">
     <option value="ville 3">Ville 3</option>
     <option value="ville 4">Ville 4</option>
   </optgroup>
</select>

Any idea ? Thank you.

Answer 1

As gp_sflover said in comments , you can use the group_by option of the entity field type :

This is a property path (eg author.name ) used to organize the available choices in groups. It only works when rendered as a select tag and does so by adding optgroup elements around options. Choices that do not return a value for this property path are rendered directly under the select tag, without a surrounding optgroup.

So, assuming region is a property of city , your code should look like this:

    ->add('city', 'entity', array(
        'empty_value' => 'Choisissez une option',
        'class' => 'FrontBundle:City',
        'query_builder' => function(EntityRepository $er) {
            return $er->createQueryBuilder('c')
                ->orderBy('c.city', 'ASC');
        },
        'group_by' => 'region',
    ))