Change Allowed Values for List Fields in Drupal 8

Beginning in Drupal 8, field settings were moved into configuration files. The idea was to easily import these settings if something happened to your database and to ensure a sort of data integrity for a field’s value. Certainly an improvement to Drupal 7 (without the Features module) way of handling field settings.

What is the client wants to change the field’s setting after data has already been entered? Unless you’re adding a new item (while the existing list items remain the same), you’ll need to override the list values using a function in the global namespace. This option allows for dynamic values but requires future changes to be made in this function.

Steps to alter field values#

Step 1: Create module using Drupal Console to contain global override function

    

        BASH
        Copy to clipboard
    
    
        
  drupal generate:module

    

Note: Make sure to include a .module file

2: Add the global function in the module’s .module file

    

        PHP
        Copy to clipboard
    
    
        
  <?php

  use Drupal\field\Entity\FieldStorageConfig;
  use Drupal\Core\Entity\ContentEntityInterface;
  
  /**
   * Set dynamic allowed values for the background color field.
   */
   function custom_module_list_values(FieldStorageConfig $definition, ContentEntityInterface $entity = NULL, $cacheable) {
     return [
       'one' => 'One',
       'two' => 'Two',
       'three' => 'Three',
     ];
   }

    

Step 3: Find the configuration file and add the global function

In your project’s synced configuration folder, look for the field’s storage configuration. The name would look something like field.storage.paragraph.field_name_of_your_field.yml.

Inside the storage configuration file, look for the allowed_values_function key. Add the global function’s name to replace the existing values with the new list array.

    

        YAML
        Copy to clipboard
    
    
        
  allowed_values_function: custom_module_list_values