class FieldInstancePerViewMode

class FieldInstancePerViewMode extends FieldInstance {
    
    /**
     * {@inheritdoc}
     */
    protected function initializeIterator() {
        $instances = parent::initializeIterator();
        $rows = [];
        foreach ($instances->getArrayCopy() as $instance) {
            $data = unserialize($instance['data']);
            foreach ($data['display'] as $view_mode => $formatter) {
                $rows[] = array_merge($instance, [
                    'view_mode' => $view_mode,
                    'formatter' => $formatter,
                ]);
            }
        }
        return new \ArrayIterator($rows);
    }
    
    /**
     * {@inheritdoc}
     */
    public function fields() {
        return array_merge(parent::fields(), [
            'view_mode' => $this->t('The original machine name of the view mode.'),
            'formatter' => $this->t('The formatter settings.'),
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getIds() {
        return [
            'entity_type' => [
                'type' => 'string',
            ],
            'bundle' => [
                'type' => 'string',
            ],
            'view_mode' => [
                'type' => 'string',
            ],
            'field_name' => [
                'type' => 'string',
            ],
        ];
    }

}