interface FieldDefinitionListenerInterface

interface FieldDefinitionListenerInterface {
    
    /**
     * Reacts to the creation of a field.
     *
     * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
     *   The field definition created.
     */
    public function onFieldDefinitionCreate(FieldDefinitionInterface $field_definition);
    
    /**
     * Reacts to the update of a field.
     *
     * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
     *   The field definition being updated.
     * @param \Drupal\Core\Field\FieldDefinitionInterface $original
     *   The original field definition; i.e., the definition before the update.
     */
    public function onFieldDefinitionUpdate(FieldDefinitionInterface $field_definition, FieldDefinitionInterface $original);
    
    /**
     * Reacts to the deletion of a field.
     *
     * Stored values should not be wiped at once, but marked as 'deleted' so that
     * they can go through a proper purge process later on.
     *
     * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
     *   The field definition being deleted.
     */
    public function onFieldDefinitionDelete(FieldDefinitionInterface $field_definition);

}