Symfony2 multiple Entities of same class in one Form

I want to render a form which has multiple Entities of same Class. I will display 2 fields, Price(type=text) and Enabled(type=checkbox).

I don't know how many I will have of those entities, so form will have to get they dynamically.

I have tried to do the following

public function buildForm(FormBuilderInterface $builder, array $options)
    {

        $builder
            ->add('price', 'text', array(
                'label' => 'Price',
                'required' => true
            ))
            ->add('enabled','checkbox',array(
                'label'     => 'Use this currency',

            ))
        ;    
}

public function setDefaultOptions(OptionsResolverInterface $resolver)
{
    $resolver->setDefaults(array(
        'data_class'        => 'Osiris\Entity\Pricing',
        'csrf_protection'   => false
    ));
}

public function getName()
{
    return 'pricingtype';
}
}

And in my Controller I create my form as follows:

$pricingForm = $this->createFormBuilder($prices)
               ->add('items','collection',array(
                   'required' => false,
                   'prototype' => true,
                   'type'    => new PricingType(),
               ))
                ->getForm()
            ;

In my twig I do:

{% for price in form_pricing %}
                    <h2>Price</h2>
                    <div class="row">{{ form_widget(price) }}</div>
                {% endfor %}

However it comes only with h2 Prices and empty div with class=row. I feel like I am half way there, but I've no idea how to move on. If someone knows how to get fields on submit as well, I will really appreciate it.