Method VisitField

cpp/src/arrow/integration/json_internal.cc:192–232

  }

  Status VisitField(const std::shared_ptr<Field>& field, FieldPosition field_pos) {
    writer_->StartObject();

    writer_->Key("name");
    writer_->String(field->name().c_str());

    writer_->Key("nullable");
    writer_->Bool(field->nullable());

    const DataType* type = field->type().get();
    std::vector<std::pair<std::string, std::string>> additional_metadata;
    if (type->id() == Type::EXTENSION) {
      const auto& ext_type = checked_cast<const ExtensionType&>(*type);
      type = ext_type.storage_type().get();
      additional_metadata.emplace_back(kExtensionTypeKeyName, ext_type.extension_name());
      additional_metadata.emplace_back(kExtensionMetadataKeyName, ext_type.Serialize());
    }

    // Visit the type
    writer_->Key("type");
    writer_->StartObject();
    RETURN_NOT_OK(VisitType(*type));
    writer_->EndObject();

    if (type->id() == Type::DICTIONARY) {
      const auto& dict_type = checked_cast<const DictionaryType&>(*type);
      // Ensure we visit child fields first so that, in the case of nested
      // dictionaries, inner dictionaries get a smaller id than outer dictionaries.
      RETURN_NOT_OK(WriteChildren(dict_type.value_type()->fields(), field_pos));
      ARROW_ASSIGN_OR_RAISE(const int64_t dictionary_id,
                            mapper_.GetFieldId(field_pos.path()));
      RETURN_NOT_OK(WriteDictionaryMetadata(dictionary_id, dict_type));
    } else {
      RETURN_NOT_OK(WriteChildren(type->fields(), field_pos));
    }

    WriteKeyValueMetadata(field->metadata(), additional_metadata);
    writer_->EndObject();

    return Status::OK();
  }

  Status VisitType(const DataType& type);