How to reuse "functional code" in multiple twig files

Question

I usually load and prepare data before calling a certain include. That data may be loaded in a certain way for different cases, so I cannot add that data preparation code into the include itself. I have to do it before calling it. Like:

{# Example #}
{% set whatever = entry.whatever.one() %}
{% if whatever %}
    {% include '/_includes/whatever' with {
        'whatever': whatever
    } %}
{% endif %}

Of course there will be more complex situations, this is just an example.

If I move the {% set whatever = entry.whatever.one() %} line into its own include and then do:

{# Example #}
{% include '/_includes/prepare-whatever' %}
{% if whatever %}
    {% include '/_includes/whatever' with {
        'whatever': whatever
    } %}
{% endif %}

The scope stays inside the include, so whatever is not defined when I need it.

How can I achieve the same functionality, to stay DRY?

Thanks!

Answer 1

As Steve mentioned, there are a few different approaches, but for me I'd reach for embed in this situation. https://twig.symfony.com/doc/3.x/tags/embed.html

By combining with the parent() function, you can effectively prepend or append your per-instance data-prepping chunks of code to the output like this:

{# calling template: #}

{% embed '_includes/whatever' %}
    {% block content %}
        {# prepare some data for this instance here #}
        {% set something = 'aaa' %}

        {# include the shared portion of the `content` block via parent() #}
        {{ parent() }}
    {% endblock %}
{% endembed %}

{# _includes/whatever: #}

{% block content %}
    <h2>Hi there</h2>
    {{ something ?? null }}
{% endblock %}

Answer 2

You can't pass a variable from an included template back to the template that called it.

But you still have at least three options (that I can think of) to achieve the kind of reusability that you're looking for.

Option 1

Re-organize your code so that 'prepare-whatever' takes place in your main template, and you then include the contents of your other file which can decide whether or not it even needs to render anything.

index.twig

{% set whatever = entry.whatever.one() ?? null %}
{% include '_includes/whatever' with {
    'whatever': whatever
} %}

_includes/whatever.twig

{% if whatever %}
    Whatever: {{whatever}}
{% endif %}

Option 2

Use the extends functionality to keep important pieces of common code inside a base template, that your index.twig extends from.

index.twig

{% extends '_includes/prepare-things' %}

{% block content %}
    {% include '_includes/whatever' with {
        'whatever': whatever
    } %}
{% endblock %} 

_includes/whatever.twig

{% if whatever %}
    Whatever: {{whatever}}
{% endif %}

_includes/prepare-things

{% set whatever  = entry.whatever.one()  ?? null %}
{% set something = entry.something.one() ?? null %}

{% block content %}{% endblock %}

Option 3

Similar to option 2, except instead of extending a template from you main twig file, you can extend a template from within an included template.

index.twig

{% include '_includes/whatever' %}

_includes/whatever.twig

{% extends 'includes/prepare-whatever' %}

{% block whateverContent %}
    {% if whatever %}
        Whatever: {{whatever}}
    {% endif %}
{% endblock %}

_includes/prepare-whatever.twig

{% set whatever = entry.whatever.one() ?? null %}

{% block whateverContent %}{% endblock %}