Dynamically add elements to a form in Symfony2.1 with it still being valid?

Question

I have a form submitting a quizz to a user, and according to their answers I may want to ask them additionnal questions that I would have to dynamically add to said form.

What I have been doing so far is that I have stripped the questions that needs to be triggered by user answers (identified by a 'triggerQuestionId' attribute containing the id of the question that needs to be answered for them to be displayed) out of the questions list of the quizz, created a form and sent it to my view in twig to display the original questions to the user like so :

    <table>
        <tbody id="table_body">
            {% for answer in form.answers %}
                    <tr id={{ answer.vars.value.question.id }}>
                        <td><span class="question">{{ answer.vars.value.question.title }}</span></td>               
                        <td class="answer">
                            {{ form_widget(answer.choice) }}
                        </td>
                    </tr>                  
            {% endfor %}
        </tbody>
    </table>
    {{ form_rest(form) }}

I use an Ajax request to check if any question should be displayed when the user selects an answer to a question, and if so I create a new tr element similar to the above for the triggered question and add it to the table.

However, after posting the form, I (logically) get the following error : "ERROR: This form should not contain extra fields."

So I figured I would originally load every question and only display in the view those with 'triggerQuestionId' set at null.

But that isn't working either because if I keep {{ form_rest(form) }} in, the triggered questions are displayed, and if I don't I get an error saying that the CSRF token is invalid.

I am still a newbie regarding Symfony and I feel like there must be a much easier way that I don't know or haven't thought about.

I hope I have made myself clear enough, but do not hesitate to ask for precisions if needed.

Thanks in advance

Answer 1

Look into the collection Field Type.

There you find and example to dynamically add fields to an existing form via jQuery.