User error: "1" is an invalid render array key in Drupal\Core\Render\Element::children()

Question

I want to print "your_variable" (array) in my twig template, but i have errors.

I have .theme in my theme :

function MYTHEME_preprocess_views_view_fields(&$vars) {
   $tempstore = \Drupal::service('user.private_tempstore')->get('evenementrimouski');
   $some_data = $tempstore->get('nid');
   $vars['your_variable'][] = array(3,4,5,6);
}

My "views-view-field" twig :

{% for  value in your_variable %}
    {{ value }}
{% endfor %}

The code work but i have errors :

User error: "0" is an invalid render array key in Drupal\Core\Render\Element::children() (line 97 of core/lib/Drupal/Core/Render/Element.php).

User error: "1" is an invalid render array key in Drupal\Core\Render\Element::children() (line 97 of core/lib/Drupal/Core/Render/Element.php).

Someone have idea to resolve this problem ?

I use Drupal 8

Answer 1

Remove the brackets after the ['your_variable'] part as your variable holds only 1 array:

function MYTHEME_preprocess_views_view_fields(&$vars) {
   $tempstore = \Drupal::service('user.private_tempstore')->get('evenementrimouski');
   $some_data = $tempstore->get('nid');
   $vars['your_variable'] = [3,4,5,6];
}

Also use the short array syntax. It's part of the new coding standards: https://www.drupal.org/node/2135291

Answer 2

To answer your question, the error you are seeing is because $vars['your_variable'] is an array containing an array. var_dump($vars) would output the following.

array(1) {
  ["your_variable"]=>
  array(1) {
    [0]=>
    array(4) {
      [0]=>
      int(3)
      [1]=>
      int(4)
      [2]=>
      int(5)
      [3]=>
      int(6)
    }
  }
}

In that case, the array is expected to be a render array. That is way you get the error you see.

I assume you aren't showing the code you are using, though, since defining a literal array in a preprocess function to print it with Twig doesn't make much sense. At least, you could do that directly in Twig.

{% set your_variable = [3, 4, 5, 6] %}
{% for  value in your_variable %}
    {{ value }}
{% endfor %}

Does $tempstore->get('nid') returns an array of integers that you need to assign to $vars['your_variable'], and print it with Twig? Just use the following code.

function MYTHEME_preprocess_views_view_fields(&$vars) {
   $tempstore = \Drupal::service('user.private_tempstore')->get('evenementrimouski');
   $vars['your_variable'] = $tempstore->get('nid');
}

Are you creating an array of integers by merging different arrays of integers? Merge $vars['your_variable'] with the other arrays.

// Before you initialize $vars['your_variable'] to an empty array.
// $vars['your_variable'] = [];
$vars['your_variable'] = array_merge($vars['your_variable'], $your_other_array_of_integers);

Are you adding integers to $vars['your_variable'], which will be an array of integers?

// Before you initialize $vars['your_variable'] to an empty array.
// $vars['your_variable'] = [];
$vars['your_variable'][] = $your_integer;

Answer 3

Often is a situation that you would need to iterate an array by keys, so in this context, be sure to create the multidimensional array ( keep the appended [] ) and then use a key to iterate, such as:

{% for key,collection in collections %}
  <div>
    {{ collection[key] }}
  </div>
{%  endfor %}

And the preprocess function would look something very similar as written in the original question where 'your_variable' in this case would be collections, and the collections array would be populated using a for/foreach within that function such as:

 function mytheme_preprocess_node(&$vars) { 
   $collection = $vars['content']['field_story']; 
   $item_count = $collection['#items']->count(); 
   for ($i=0 ; $i < $item_count ; $i++) { 
     $vars['story_title'][] = $collection[$i]['#title']; 
   } 
 }

...