c++ - 如何将 bsoncxx::document::element 写入控制台

Question

我有 following function在给定键序列时从 BSON 文档中获取值:

bsoncxx::document::element deepFieldAccess(bsoncxx::document::view bsonObj, const std::vector<std::string>& path) {

    if (path.empty())
        return {};

    auto keysIter = path.begin();
    const auto keysEnd = path.end();

    auto currElement = bsonObj[*(keysIter++)];
    while (currElement && (keysIter != keysEnd))
        currElement = currElement[*(keysIter++)];

    return currElement;
}

返回的bsoncxx::document::element可以包含任何类型的值(int32、document、array、utf8 等)。如何通过 std::cout 将此元素写入控制台？

理想情况下，我只需要做:

bsoncxx::document::element myElement = deepFieldAccess(bsonObjView, currQuery);
std::cout << myElement << std::endl;

Answer 1

我们不能打印bsoncxx::document::element，但是我们可以打印bsoncxx::document::view。因此，只需将一个转换为另一个并清理生成的字符串。它既丑陋又低效，但可以快速查找 bsoncxx::document::element 的值。

std::string turnQueryResultIntoString(bsoncxx::document::element queryResult) {

    // check if no result for this query was found
    if (!queryResult) {
        return "[NO QUERY RESULT]";
    }

    // hax
    bsoncxx::builder::basic::document basic_builder{};
    basic_builder.append(bsoncxx::builder::basic::kvp("Your Query Result is the following value ", queryResult.get_value()));

    // clean up resulting string
    std::string rawResult = bsoncxx::to_json(basic_builder.view());
    std::string frontPartRemoved = rawResult.substr(rawResult.find(":") + 2);
    std::string backPartRemoved = frontPartRemoved.substr(0, frontPartRemoved.size() - 2);

    return backPartRemoved;
}