Field Class Dependencies

Question

The question is pretty straightforward. How can I add a class on field A, if field B is empty? I can not find any module does this feature. The Conditional Fields does not have the class feature too. Can this done by programmatically? If so, how?

Answer 1

One solution here is is to use template_preprocess_field function. In your template.php add a MYTHEME_preprocess_field function and perform a check on the node's field value to determine a class that you set in the classes_array variable.

function MYTHEME_preprocess_field(&$variables) {
  $node = menu_get_object();

  //Add a new CSS class to field_MYHIDDEN_FIELD
  if($variables['element']['#field_name'] == 'field_MYHIDDEN_FIELD') {

    //Check field_MYCHECKED_FIELD for an empty value
    $new_class = (!isset($node->field_MYCHECKED_FIELD[LANGUAGE_NONE][0]['value'])) ? 'mytheme-field-novalue' : 'mytheme-field-value';
    $variables['classes_array'][] = $new_class;
  }
}

Answer 2

I would use states for something like this:

https://api.drupal.org/api/drupal/developer!topics!forms_api_reference.html/7#states

Answer 3

Another more pure UI route is to use Views, Views "No Results" and View "Rewriting" and either the EVA or ctools Content Panels to construct the node view.

I haven't tested this, but it will look something like this:

1. Create a content view filtering by node and published value
2. Add fields B and A (in that order)
3. Set Field A to "Exclude from Display"
4. Configure field B's "No results behavior" to render something like <span class="b_empty">[field_a]</span> but set the "Rewrite Results" to <span class="b_has_data">[field_a]</span><span>[field_b]</span> Here, field B is doing all the heavy lifting, empty or not.
5. Using EVA, you can then attach that result to your node's field display as you need.