Additional fields for Ubercart uc_order_product

Question

I need to add fields to the Ubercart entity uc_order_product. I was looking into the function field_create_instance, but don`t know exactly where to use it. I believe I should attach the field I want to the uc_order_product entity using field_create_instance.

The 'uc_order_product' definition in uc_order.module doesn't have a fieldable => TRUE definition. May I add that definition from my custom module and tell uc_order_product is fieldable? This is uc_order_product entity definition in the uc_order.module.

'uc_order_product' => array(
  'label' => t('Order product'),
  'base table' => 'uc_order_products',
  'controller class' => 'UcOrderProductController',
  'metadata controller class' => 'UcOrderProductMetadataController',
  'entity keys' => array(
    'id' => 'order_product_id',
    'label' => t('Order product'),
  ),
  'bundles' => array(
    'uc_order_product' => array(
      'label' => t('Order product'),
    ),
  ),
  'view modes' => array(
    'full' => array(
      'label' => t('Normal view'),
    ),
    'cart' => array(
      'label' => t('Cart view'),
    ),
  ),
  // Entity API callbacks.
  'access callback'   => 'uc_order_order_product_access',
  'save callback'     => 'uc_order_product_entity_save',
  'deletion callback' => 'uc_order_product_delete',
) 

Finally, I am trying to hook to this entity when it gets updated (hook_entity_update, hook_entity_presave) but they never get called on uc_order_product update. How can I hook to this entity when it is being saved, or when it has been saved? Thank you!

Answer 1

First of all, if you want alter the meta information of an entity, the hook_entity_info_alter in your custom module is the right way. More information in official page: hook_entity_info_alter

In this particular case, attributte 'fieldable' is not defined, so the function responsable to call the hook_entity_info and hook_entity_info_alter is the entity_get_info() in common.inc file. This function provide default values and the default value to 'fieldable' is FALSE. You only need change this value implementing hook_entity_info_alter.

 function YOUR_MODULE_entity_info_alter(&$entity_info){
   if(isset($entity_info['uc_order_product'])){
     $entity_info['uc_order_product']['fieldable'] = TRUE;
   }
 }

Second issue, This is a link to a previous question about how create fields programatically. The best answer suggests field_create_fieldand 'field_create_instance', but if you have a defined field (for example, an image type field created through the UI), you could use field_update_field and 'field_update_instance'. You can find more information about these functions in field.crud.inc in the field module folder.