Read field value from $variables in hook_preprocess_html()

Question

I want to get a field value from a node that I can use in the html--front.html.twig template file.
I can create a new variable, for example with $variables['custom_twig_variable'] = 'Some important value';.

Then in the template file, I would simply get that value with {{ custom_twig_variable }}.

I don't know how to get the field value from $variables, the argument passed to the theme hook, whose content is the following one.

Array (
  [user] => Drupal\Core\Session\AccountProxy Object (
    [requestStack:protected] => Symfony\Component\HttpFoundation\RequestStack Object (
      [requests:Symfony\Component\HttpFoundation\RequestStack:private] => Array (
        [0] => Symfony\Component\HttpFoundation\Request Object (
          [attributes] => Symfony\Component\HttpFoundation\ParameterBag Object (
            [parameters:protected] => Array (
              [_system_path] => node/4
              [_controller] => \Drupal\node\Controller\NodeViewController::view
              [_title_callback] => \Drupal\node\Controller\NodeViewController::title
              [node] => Drupal\node\Entity\Node Object (
                [values:protected] => Array (
                  [vid] => Array (
                      [x-default] => 4
                  )
                  [field_background_color] => Array (
                    [x-default] => Array (
                      [0] => Array (
                        [value] => ff00ff
                      )
                    )
                  )
                )
              )
            )
          )
        )
      )
    )
  )
)

How do I get the value of field_background_color?

Answer 1

So your field is on the node?

Then you need to get the node object first.

<?php
if (($node = \Drupal::routeMatch()->getParameter('node')) && $node instanceof \Drupal\node\NodeInterface) {

}

Once you have that, you can read your field, assuming it is a text field, like this: $node->field_background_color->value. Make sure to always check if you really have a $node object as done in the snippet above when you're in the global context. You will only have on on node/N, but not on other pages.

There are many questions already about how to access field values, and there are great presentations as well.

Answer 2

Simply iterate the $variables['view']->result array and get every field value you want.

foreach ($variables['view']->result as $key=>$result){
    $field = $result->_entity->get('field_name')->getValue();
    $variables['rows'][$key]['var_name'] = $field[0]['value']; 
}

In this line $variables['rows'][$key]['var_name'] = $field[0]['value']; you save the data into the row-variable where you can access it later in your twig-template with {{row.var_name}}

Answer 3

You have entity values at hand

$element = $variables['element'];
if ( $entity = $element['#object'] ) {
  dump ($entity); 
  exit;
}