index.html.twig

{% extends 'AcmeDemoBundle::layout.html.twig' %}

{% block title "Form test" %}
{% form_theme form.questions _self %}

{% block content %}
    <form action="" method="POST">
        {{ form_rest(form) }}
        <input type="submit" value="Send" />
    </form>
{% endblock %}

{% block _tp_assignment_questions_row %}
    <div class="collection">
        <a class="add_item" data-prototype="{{ form_row(form.vars.prototypes.open_question) | escape }}" href="#">+ open question</a>
        <a class="add_item" data-prototype="{{ form_row(form.vars.prototypes.choice_question) | escape }}" href="#">+ choice question</a>

        {{ form_widget(form) }} {# Note that this generates <div id="tp_assignment_questions"> which is used in the Javascript #}
    </div>
    <script type="text/javascript">
        if (!window.$) alert('jQuery not loaded');
        $(function() {
            if (!window.infinite || !window.infinite.Collection) alert('Collections helper not loaded');
            var questions = $('#tp_assignment_questions');
            new window.infinite.Collection(questions, questions.siblings('.add_item'));
        });
    </script>
{% endblock %}

{% block open_question_row %}
    <div class="item">
        <h4>Open Question <a class="remove_item" href="#">Remove</a></h4>
        {{ form_widget(form) }}
    </div>
{% endblock %}

{% block choice_question_row %}
    <div class="item">
        <h4>Choice Question <a class="remove_item" href="#">Remove</a></h4>
        {{ form_widget(form) }}
    </div>
{% endblock %}

OpenQuestionType.php

<?php

namespace Acme\DemoBundle\Form;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

class OpenQuestionType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('_type', 'hidden', array(
            'data'   => $this->getName(),
            'mapped' => false
        ));
    }

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

    public function getParent()
    {
        return 'question';
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'Acme\DemoBundle\Model\OpenQuestion',
            'model_class' => 'Acme\DemoBundle\Model\OpenQuestion',
        ));
    }
}

TpAssignment.php

<?php

namespace Acme\DemoBundle\Form;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;

class TpAssignmentType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('title', 'text');

        $builder->add('questions', 'infinite_form_polycollection', array(
            'types' => array('choice_question', 'open_question'),
            'allow_add' => true,
            'allow_delete' => true,
            'by_reference' => false,
        ));
    }

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

Hello again and thanks for support.

I almost get it to work, Displaying results looks like to be blank with "form_widget(form._type)"

Rendering ->

With {% for subForm in form %} {{ dump(subForm) }} {% endfor %} - (data is displayed in dump)

With dump inside ..._entry_row -> {{ dump(form._type) }} - no moyensComm data inside