How to use MongoDB GeoSpatial Index in C++ -

in python, pymongo provides nice support mongodb geospatial index. however, c++ when use mongocxx in c++, little bit confused grammar.

for example, in python (pymongo) used

cursor = db.colection.find(     {         "loc": {             "$near": [lon, lat]         }     } ).limit(10) 

to nearest 10 items given location. how can same thing in c++?

i tried:

mongocxx::cursor cursor = coll.find(document{} << "loc" << open_document <<                                     "$near" << [lon, lat]                                     << close_document << finalize); 

i not sure if correct approach, , failed set number of results.

could give me instructions on geospatial index in c++? documents/examples highly apreciated.

thank much.

you can use mongocxx::options::find::limit. check mongocxx::collection::find. following should work :

mongocxx::options::find opts; opts.limit(10);  mongocxx::cursor cursor = coll.find(document{} << "loc" << open_document      << "$near" << bsoncxx::builder::stream::open_array      << lon << lat << bsoncxx::builder::stream::close_array      << close_document << finalize, opts);