Twig variable variable

Question

There are some Twig arrays:

feeds, where a feed gets category_name;
events, news, announces with posts.

Therefore, I can get posts for a category that way:

{% for feed in feeds %}
  {% if feed.category_name == "events" %}
  {% for post in events %}
    {{post.title}}
  {% endfor %}
  {% endif %}
{% endfor %}

Can I get the same output (as above one loop returns) with category_name string set as array name?

Here feed.category_name returns events:

{% for feed in feeds %}
  {% for post in feed.category_name %} {# feed.category_name == "events" #}
    {{post.title}}
  {% endfor %}
{% endfor %}

@JCSama I want to loop the array that has the same name as category_name. — A. Z.
– A. Z., Commented Mar 17, 2015 at 14:00
I'm not sure I get it, you have have a string category_name and you wanna loop on it !! — JC Sama
– JC Sama, Commented Mar 17, 2015 at 14:18

Denis Mysenko · Accepted Answer · 2015-03-17 15:06:09Z

2

I think what the question author means is – access the array using a name derived from another variable. So that extra conditions are not necessary (and most answers here do propose extra conditions).

Based on my several-minute-research, Volt alone won't let you do it. However, since you can embed PHP code in Volt templates and twig files are compiled to PHP later on anyway, you could do something like:

{% for feed in feeds %}
  <?php foreach (${$feed.category_name} as $post) { ?>
    {{post.title}}
  <?php } ?>
  {% endif %}
{% endfor %}

I have already tested this – it does work. You may want to add an extra check if the array exists, to avoid warnings:

{% for feed in feeds %}
  <?php 
    if (!empty(${$feed.category_name})) { 
      foreach (${$feed.category_name} as $post) { 
  ?>
          {{post.title}}
  <?php } } ?>
  {% endif %}
{% endfor %}

If you don't like the idea of embedding PHP in your template – don't forget that your template is going to be compiled as PHP anyway!

answered Mar 17, 2015 at 15:06

Denis Mysenko

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2 Comments

A. Z. Over a year ago

Thanks for your solution. Unfortunately, in my environment (WordPress Timber plugin) I can't use PHP in Twig templates.

Denis Mysenko Over a year ago

Then, I guess, you won't be able to do it the perfect way :-( You will have to manually parse every category name, like others proposed

Matias Kinnunen · Accepted Answer · 2018-01-18 14:37:37Z

1

The global variable _context holds all variables in the current context, so you can do this:

{% for feed in feeds %}
    {% for post in _context[feed.category_name]|default(null) %}
        {{ post.title }}
    {% endfor %}
{% endfor %}

The |default(null) is required to prevent Twig from throwing an exception if the variable is not found.

See TwigFiddle

answered Jan 18, 2018 at 14:37

Matias Kinnunen

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Comments

qrazi · Accepted Answer · 2015-03-17 14:40:57Z

0

You want the conditional to be "added" to the loop? I think you mean this in Twig Documentation:

<ul>
    {% for user in users if user.active %}
        <li>{{ user.username|e }}</li>
    {% endfor %}
</ul>

Edit Your main issue was with the "variable variable". You can solve this with the attribute() function and combining the different feeds into one assoc array (categories?).

So perhaps something like (untested):

{% for feed in feeds %}
  {% for post in attribute(categories, feed.category_name) %}
    {{post.title}}
  {% endfor %}
{% endfor %}

edited Mar 17, 2015 at 14:40

answered Mar 17, 2015 at 13:51

qrazi

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2 Comments

A. Z. Over a year ago

Thanks for your idea. I combined events and news arrays into new one (all_posts) and with {% for post in all_posts if post.has_term( feed.category_name ) %}[[post.title]]{% endfor %} I can now get posts of the category.

A. Z. Over a year ago

This workaround has helped with my issue. However, it is not exactly related to variable variable topic.

JC Sama · Accepted Answer · 2015-03-17 14:47:27Z

0

Based on your comment :

{% set new_array = news|merge(events) %}
{% for feed in feeds if attribute(feed.category_name, ['events', 'news']) %}
     {% for post in new_array %}
         {{post.title}}
     {% endfor %}
  {% endif %}
{% endfor %}

edited Mar 17, 2015 at 14:47

answered Mar 17, 2015 at 14:34

JC Sama

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