Entity Type Inheritance?

When I first started working with Entities, this is exactly what I initially assumed they could do. I was disheartened when I found out there was only one level of inheritance Entity -> bundle. I had my heart set on Entity -> first level inherited entity -> second level inherited entity -> .. and so on. I also thought that an entity would surely inherit all of its "parents" fields. Again I was disappointed to find out only properties were inherited and entity types were not fieldable ... just plain old boring one dimensional properties!

Anyway, I agree in theory this would be awesome. Any ideas how it could be accomplished given the current framework provided in core and entity api?

I haven't really given the field stuff much thought. At first reading your comment above I didn't think that there was much we could do to make it simpler then it already is, but scanning through the process again I am seeing possibilities.

So I guess there is quite a bit that could be abstracted into a single function for adding fields. However I think it would require that either a) we create a default abstraction function for each field type out there, or b) we add an api to ECK to allow field module developers to incorporate it into their modules.

For example with a complicated field like a taxonomy term reference you currently would have to do the following, assuming you are also creating a taxonomy:

  // Create a vocabulary for notification terms.
  $vocabulary = (object) array(
    'name' => t('Notification terms'),
    'description' => t('Use Notification terms to categorize content for instant notifications.'),
    'machine_name' => 'notifications_terms',
    'help' => t('Enter a comma-separated list of terms.'),
  );
  taxonomy_vocabulary_save($vocabulary);
  // Create a term reference field using the vocabulary.
  $field = array(
    'field_name' => 'field_' . $vocabulary->machine_name,
    'type' => 'taxonomy_term_reference',
    // Set cardinality to unlimited for tagging.
    'cardinality' => FIELD_CARDINALITY_UNLIMITED,
    'settings' => array(
      'allowed_values' => array(
        array(
          'vocabulary' => $vocabulary->machine_name,
          'parent' => 0,
        ),
      ),
    ),
  );
  field_create_field($field);
  // Add an instance of the term reference field to the article node type.
  $instance = array(
    'field_name' => 'field_' . $vocabulary->machine_name,
    'entity_type' => 'node',
    'label' => 'Notification terms',
    'bundle' => 'article',
    'description' => $vocabulary->help,
    'widget' => array(
      'type' => 'taxonomy_autocomplete',
      'weight' => -4,
    ),
    'display' => array(
      'default' => array(
        'type' => 'taxonomy_term_reference_link',
        'weight' => 10,
      ),
      'teaser' => array(
        'type' => 'taxonomy_term_reference_link',
        'weight' => 10,
      ),
    ),
  );
  field_create_instance($instance);

I can definitely see that we could abstract that process down to something like

  // Create a vocabulary for notification terms.
  $vocabulary = (object) array(
    'name' => t('Notification terms'),
    'description' => t('Use Notification terms to categorize content for instant notifications.'),
    'machine_name' => 'notifications_terms',
    'help' => t('Enter a comma-separated list of terms.'),
  );

  $options = array(
    'settings' => array(
      'allowed_values' => array(
        array(
          'vocabulary' => $vocabulary->machine_name,
          'parent' => 0,
        ),
      ),
    ),
  );
$bundle->addfield('taxonomy_term_reference', $options);

That would be cool!!

Got inspired this morning. Here is a start anyway. I just wrote it one off and did no testing whatsoever, I think its pretty complete in terms of what would be needed for a addField() function.

I am currently trying to find out what the best way is to handle fields which are common to multiple bundles. I am wondering whether it might be possible to somehow specify a set of fields for an entity-type, and automatically have them added to all bundles of that entity type.

An example would be a "product" entity type and a "price" field, which is automatically added to all "product bundles".

Is this issue working towards this use case, or would that be something else?

Okay, thanks for the explanation.

cool!

I´ve created a sandbox project with another approach.
There´s a modul "Bundle Inharitance". For this I created a tiny module.

Corresponding issue: https://drupal.org/node/2125065
Sandbox Project: https://drupal.org/sandbox/kasalla/2125031