如何将 rapidjson::Value 转化为string类型

                                rapidjson::Value msg(rapidjson::kObjectType); 
				rapidjson::StringBuffer  buffer;
				rapidjson::Writer  writer(buffer);
				rapidjson::Document document ;
				rapidjson::Document::AllocatorType & allocate = document.GetAllocator();
				document.SetObject();//重点
				msg.AddMember("uid2",112,allocate);
				msg.AddMember("test2",113,allocate);
				document.AddMember("info",msg,allocate);
				document.Accept(writer);
				auto msgToString = buffer.GetString();
				log("info:%s",msgToString);