I am trying to use mongodb with latest c++ driver following this example as reference.
My code is as follows:
#include <mongocxx/client.hpp>
#include <mongocxx/options/find.hpp>
#include <mongocxx/instance.hpp>
#include <mongocxx/uri.hpp>
using bsoncxx::builder::stream::document;
using bsoncxx::builder::stream::open_document;
using bsoncxx::builder::stream::close_document;
using bsoncxx::builder::stream::open_array;
using bsoncxx::builder::stream::close_array;
using bsoncxx::builder::stream::finalize;
class MongoDBApiUtils {
public :
MongoDBApiUtils(){}
static json validateDoc(const std::string& key ,const json& regInfo);
static json validatePreRegistration(const json& regInfo);
static bool checkUserExist(const json& regInfo);
static bool checkUserBlackList(const json& regInfo);
/*
* Retrieves a latest block from blockchain, based on the
* given query field. It is assumed that the database is
* indexed on the queryField, to avoid O(n) problem.
**/
static json getLatestBlock(
const mongocxx::database& db, const std::string& filter) {
auto cursor = db["ctlblocks"].find_one(document{} << filter << finalize);
}
/** Creates and adds a new block into the blockchain **/
static json addBlock(json& current, const json& prev) {
}
private :
};
#endif
But I get compile errors, which I am unable to decipher. It gives error on the line, where I am trying to create a cursor, by calling the find_one method.
In file included from /Volumes/second/nvi/github/blockchain_db/src/Impl/mongo/src/mongo_db_api.cpp:3:
/Volumes/second/nvi/github/blockchain_db/src/Impl/mongo/src/mongo_db_api_utils.hpp:47:46: error: no viable conversion from 'typename std::enable_if<!util::is_functor<const finalize_type &, void (single_context)>::value, key_context<closed_context> >::type' (aka 'bsoncxx::v_noabi::builder::stream::key_context<bsoncxx::v_noabi::builder::stream::closed_context>') to 'bsoncxx::document::view_or_value' (aka 'view_or_value<document::view, document::value>')
auto cursor = db["ctlblocks"].find_one(document{} << filter << finalize);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/local/include/bsoncxx/v_noabi/bsoncxx/view_or_value.hpp:60:20: note: candidate constructor not viable: no known conversion from 'typename std::enable_if<!util::is_functor<const finalize_type &, void (single_context)>::value, key_context<closed_context> >::type' (aka 'bsoncxx::v_noabi::builder::stream::key_context<bsoncxx::v_noabi::builder::stream::closed_context>') to 'bsoncxx::v_noabi::document::view' for 1st argument
BSONCXX_INLINE view_or_value(View view) : _view{view} {
^
/usr/local/include/bsoncxx/v_noabi/bsoncxx/view_or_value.hpp:69:20: note: candidate constructor not viable: no known conversion from 'typename std::enable_if<!util::is_functor<const finalize_type &, void (single_context)>::value, key_context<closed_context> >::type' (aka 'bsoncxx::v_noabi::builder::stream::key_context<bsoncxx::v_noabi::builder::stream::closed_context>') to 'bsoncxx::v_noabi::document::value &&' for 1st argument
BSONCXX_INLINE view_or_value(Value&& value) : _value(std::move(value)), _view(*_value) {
^
/usr/local/include/bsoncxx/v_noabi/bsoncxx/view_or_value.hpp:75:20: note: candidate constructor not viable: no known conversion from 'typename std::enable_if<!util::is_functor<const finalize_type &, void (single_context)>::value, key_context<closed_context> >::type' (aka 'bsoncxx::v_noabi::builder::stream::key_context<bsoncxx::v_noabi::builder::stream::closed_context>') to 'const bsoncxx::v_noabi::view_or_value<bsoncxx::v_noabi::document::view, bsoncxx::v_noabi::document::value> &' for 1st argument
BSONCXX_INLINE view_or_value(const view_or_value& other)
^
/usr/local/include/bsoncxx/v_noabi/bsoncxx/view_or_value.hpp:93:20: note: candidate constructor not viable: no known conversion from 'typename std::enable_if<!util::is_functor<const finalize_type &, void (single_context)>::value, key_context<closed_context> >::type' (aka 'bsoncxx::v_noabi::builder::stream::key_context<bsoncxx::v_noabi::builder::stream::closed_context>') to 'bsoncxx::v_noabi::view_or_value<bsoncxx::v_noabi::document::view, bsoncxx::v_noabi::document::value> &&' for 1st argument
BSONCXX_INLINE view_or_value(view_or_value&& other) noexcept
Any ideas how to go about solving this?
You aren't in the right stream context to pass finalize, since you have only provided one value to the stream. To use the stream builder, you pass a key, and then its value:
auto result = document{} << k1 << v1 << k2 << v2 << ... kn << vn << finalize
Gives you a result object holding a BSON object representing the JSON
{ 'k1' : v1, 'k2' : v2, ... 'kn' : vn }
Your code has provided only something key like, so the document stream is not in an accepting state for finalize.
If your entire filter is a JSON string, then just convert it to BSON with bsoncxx::from_json. Note also that the stream based document builders are more or less de-emphasized, due to exactly this sort of opportunity for confusion and misuse.
You may get better mileage from the basic builders.