function field_create_instance in Drupal 7

Creates an instance of a field, binding it to a bundle.

Parameters

$instance: A field instance definition array. The field_name, entity_type and bundle properties are required. Other properties, if omitted, will be given the following default values:

label: the field name
description: empty string
required: FALSE
default_value_function: empty string
settings: each omitted setting is given the default value specified in hook_field_info().
widget:
- type: the default widget specified in hook_field_info().
- settings: each omitted setting is given the default value specified in hook_field_widget_info().
display: Settings for the 'default' view mode will be added if not present, and each view mode in the definition will be completed with the following default values:
- label: 'above'
- type: the default formatter specified in hook_field_info().
- settings: each omitted setting is given the default value specified in hook_field_formatter_info().
View modes not present in the definition are left empty, and the field will not be displayed in this mode.

Return value

The $instance array with the id property filled in.

Throws

FieldException

See: Field API data structures.

File

modules/field/field.crud.inc, line 473: Field CRUD API, handling field and field instance creation and deletion.

Code

function field_create_instance($instance) {
  $field = field_read_field($instance['field_name']);
  if (empty($field)) {
    throw new FieldException(t("Attempt to create an instance of a field @field_name that doesn't exist or is currently inactive.", array(
      '@field_name' => $instance['field_name'],
    )));
  }

  // Check that the required properties exists.
  if (empty($instance['entity_type'])) {
    throw new FieldException(t('Attempt to create an instance of field @field_name without an entity type.', array(
      '@field_name' => $instance['field_name'],
    )));
  }
  if (empty($instance['bundle'])) {
    throw new FieldException(t('Attempt to create an instance of field @field_name without a bundle.', array(
      '@field_name' => $instance['field_name'],
    )));
  }

  // Check that the field can be attached to this entity type.
  if (!empty($field['entity_types']) && !in_array($instance['entity_type'], $field['entity_types'])) {
    throw new FieldException(t('Attempt to create an instance of field @field_name on forbidden entity type @entity_type.', array(
      '@field_name' => $instance['field_name'],
      '@entity_type' => $instance['entity_type'],
    )));
  }

  // Set the field id.
  $instance['field_id'] = $field['id'];

  // Note that we do *not* prevent creating a field on non-existing bundles,
  // because that would break the 'Body as field' upgrade for contrib
  // node types.
  // TODO: Check that the widget type is known and can handle the field type ?
  // TODO: Check that the formatters are known and can handle the field type ?
  // TODO: Check that the display view modes are known for the entity type ?
  // Those checks should probably happen in _field_write_instance() ?
  // Problem : this would mean that a UI module cannot update an instance with a disabled formatter.
  // Ensure the field instance is unique within the bundle.
  // We only check for instances of active fields, since adding an instance of
  // a disabled field is not supported.
  $prior_instance = field_read_instance($instance['entity_type'], $instance['field_name'], $instance['bundle']);
  if (!empty($prior_instance)) {
    $message = t('Attempt to create an instance of field @field_name on bundle @bundle that already has an instance of that field.', array(
      '@field_name' => $instance['field_name'],
      '@bundle' => $instance['bundle'],
    ));
    throw new FieldException($message);
  }
  _field_write_instance($instance);

  // Clear caches
  field_cache_clear();

  // Invoke external hooks after the cache is cleared for API consistency.
  module_invoke_all('field_create_instance', $instance);
  return $instance;
}

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