Difference between customizing form theme and referencing block in Symfony? - php

Question

what is the difference between referencing a widget block and customizing it : the docs say :
So far, to override a particular form block, the best method is to
copy the default block from form_div_layout.html.twig, paste it into a
different template, and then customize it. In many cases, you can
avoid doing this by referencing the base block when customizing it
But to me it looks the same :
{# app/Resources/views/Form/fields.html.twig #}
{% extends 'form_div_layout.html.twig' %}
{% block integer_widget %}
<div class="integer_widget">
{{ parent() }}
</div>
{% endblock %}
{# app/Resources/views/form/fields.html.twig #}
{% block integer_widget %}
<div class="integer_widget">
{% set type = type|default('number') %}
{{ block('form_widget_simple') }}
</div>
{% endblock %}
What is the difference?

Answer 1

The first example in the documentation that you are referencing shows how to override the entire widget that displays your form element.
The second example in the documentation that you are referencing shows how you can employ code re-use so that you are not rewriting form templating sections that you are not modifying. So, instead of having to declare
{% set type = type|default('number') %}
{{ block('form_widget_simple') }}
all over again in your overriding widget, you can instead reference the base block that already has this. If you are referencing base blocks from an external template, you can call the parent block via {{ parent() }}, and if you are referencing blocks from inside the same template as the form, you can call the base block via {{ block('base_integer_widget') }}
If you look at it from a PHP/Symfony point of view with inheritance that can help explain it as well. Say you have one PHP class that extends another and you want to override a function named doSomething() - you might rewrite the entire function as you need it. But, say that doSomething() has a block of common code that you always want to run, then you might perform your actions and call parent::doSomething() at the end of it. Or, if you're accessing a different Symfony service you might call $this->get('some.service')->doSomething() instead.
That's the same concept here, you can either override the entire widget or you can override parts of it - perhaps putting a surrounding <div></div> but calling {{ parent() }} from within that since you're changing nothing else about the widget.
I do have one example where I overrode standard button behavior in Symfony and used both cases. I have a separate template file in `app/Resources/views/Form/navigationButton.html.twig' with the following code:
{% use 'form_div_layout.html.twig' %}
{% block button_widget -%}
{% set attr = attr|merge({class: (attr.class|default(''))|trim}) %}
{{- parent() -}}
{%- endblock %}
{% block button_row -%}
{{- form_widget(form) -}}
{%- endblock button_row %}
I am overriding the button widget by allowing additional classes to be passed as attributes and then calling the parent widget to produce it as normal. I then override the button row widget to not put surrounding <div></div> tags since I didn't want that in my template (see the originals here and here).
Then to use in one of my templates I simply do:
{% form_theme form ':Form:navigationButton.html.twig' %}