Reuseable blocks inside of custom form themes in symfony - symfony

Question

I want to call a custom block inside an overwritten theme-block:
{% block file_widget %}
{% if image is not null %}
{{ block('imagePreview') }}
{% endif %}
{{ block('form_widget') }}
{% endblock %}
{% block imagePreview %}
<img src="{{ image.getFullPath | imagine_filter('medium_square') }}"
alt="{{ image.filename }}"/>
{% endblock %}
The imagePreview is not shown.
But it is working when I don't use a block.
And it is also working when I dont use a FormTypeExtension and create an ImageType instead.
So I guess the file_widgetblock still has the scope of the parent form_div_layout.html.twig and there in fact no imagePreview block exists.
So how can I solve this.
I mean now I solved it by removing the block.
But I just want to know if someone has a solution to this.
Maybe there is a way for using reuseable blocks inside of custom form themes in symfony?

Answer 1

Finally I found the solution:
I just did not 'use' the base template explicit.
The form theme worked without this - because symfony falls back the the base form theme when it does not find a block inside the new theme file.
But it seems then you also can not use custom blocks inside this new theme file.
So this works now:
{% use 'form_div_layout.html.twig' %}
{% block file_widget %}
{% if image is not null %}
{{ block('imagePreview') }}
{% endif %}
{{ block('form_widget') }}
{% endblock %}
{% block imagePreview %}
<img src="{{ image.getFullPath | imagine_filter('medium_square') }}"
alt="{{ image.filename }}"/>
{% endblock %}