BSONObj obj = BSONObjBuilder() .append("name", "John") .append("age", 30) .obj(); // create a BSON object with 2 fields BSONObj newObj = BSONObjBuilder() .appendElements(obj) // copy all fields from obj .append("city", "New York") .obj(); // create a new BSON object with 3 fields
#includeIn this example, we use the bsoncxx package library to create a BSON object with two fields ("name" and "age"). Then, we create a new BSON object by adding a new field ("city") using the bsoncxx::builder::stream::document class. We concatenate the existing fields from the first object using the bsoncxx::builder::stream::concatenate method. Finally, we create a BSON object with three fields using the finalize method. Overall, the BSONObj class in C++ is a useful tool for working with BSON objects, and the bsoncxx package library provides a lightweight and efficient implementation.#include using bsoncxx::builder::stream::document; using bsoncxx::builder::stream::finalize; // create a BSON object with 2 fields bsoncxx::document::value doc_value = document{} << "name" << "John" << "age" << 30 << finalize; bsoncxx::document::view doc_view = doc_value.view(); // add a new field to the BSON object bsoncxx::builder::stream::document new_doc; new_doc << "city" << "New York" << bsoncxx::builder::stream::concatenate(doc_view); // create a new BSON object with 3 fields bsoncxx::document::value new_doc_value = new_doc << finalize; bsoncxx::document::view new_doc_view = new_doc_value.view();