DocumentElement example

case 'document':
                if (!$model instanceof Document) {
                    throw new RuntimeException(sprintf('Model object is not an instance of expected class "%s"', Document::class));
                }

                if (!empty($data['id'])) {
                    $elements = new ArrayCollection();
                    foreach ($data['elements'] as $element) {
                        $elementModel = $this->getRepository('documentElement')->find($element['id']);

                        if (!$elementModel instanceof DocumentElement) {
                            $elementModel = new DocumentElement();
                            $elementModel->setDocument($model);
                        }

                        $elementModel->fromArray($element);
                        $elements->add($elementModel);
                    }
                    $data['elements'] = $elements;
                } else {
                    $data['elements'] = $this->createDocumentElements($model);
                }
                break;