Symfony 2 only override specific form inputs - php

Question

I would like to override a specific element of my Symfony form, while allowing my standard template to generate the rest of the fields. So far it has been a case of either/or.
First my template generates the form element
<form action="" method="post" {{ form_enctype(form) }} autocomplete="off">
{% form_theme form 'SuperSecretProjectBundle:Default:collection.html.twig' %}
{{ form_widget(form) }}
<input type="submit" class="right submit button primary small" value="Save" />
</form>
Inside collection.html.twig I have the following blocks: form_row is the generic widget renderer, while image_sets_row is my specific row I want to override.
{% block form_row %}
<div class="row">
<div class="large-12 columns{% if not form.vars.valid %}error{% endif %}">
{{ form_label(form) }}
{{ form_widget(form) }}
<small>{{ form_errors(form) }}</small>
</div>
</div>
{% endblock form_row %}
{% block image_sets_row %}
<div id="image_sets">
<div class="row">
<div class="columns large-12">
Add image set
</div>
</div>
</div>
{% endblock %}
This results in using form_row for all fields, without my modified block. How can I have Symfony output the elements that are not being specifically overridden and include my new blocks as well?

Answer 1

What you need is a custom field type for the field you are trying to use your custom widget for.
As shown in the link, first you need to create a custom Field Type class like so
// src/AppBundle/Form/Type/ImageSetsType.php
namespace AppBundle\Form\Type;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Symfony\Component\Form\Extension\Core\Type\ChoiceType; #should change to whatever parent type you need
class ImageSetsType extends AbstractType{
public function configureOptions(OptionsResolver $resolver){
$resolver->setDefaults( array() ); #set any option defaults you need here
}
public function getParent(){
return ChoiceType::class; #again change this to whatever parent type you need
}
}
Next we get your template for that block working properly
{# app/Resources/views/form/fields.html.twig #}
{% block imagesets_widget %}
<div id="image_sets">
<div class="row">
<div class="columns large-12">
{{ form_label(form) }}
{{ form_widget(child) }}
Add image set
<small>{{ form_errors(form) }}</small>
</div>
</div>
</div>
{% endblock %}
Then you use your newly created type in your form as you would any other.
As I assume you want a little more in