I Have A Vector Of RoomData Object Here Is The Object:
typedef struct RoomData
{
unsigned int id;
std::string name;
std::string maxPlayers;
unsigned int questionCount;
unsigned int timePerQuestion;
unsigned int isActive;
} RoomData;
I need to Convert this vector to json object. How can I do this? I Have no idea
jsoncons and nlohmann both support conversion between JSON and C++ objects, as does Martin York's ThorsSerializer (see his answer.)
Given a vector of RoomData, viz.:
namespace ns {
struct RoomData
{
unsigned int id;
std::string name;
std::string maxPlayers;
unsigned int questionCount;
unsigned int timePerQuestion;
unsigned int isActive;
} RoomData;
}
std::vector<ns::RoomData> rooms;
rooms.push_back(ns::RoomData{ 1, "Room 1", "Few", 2, 56, 1 });
rooms.push_back(ns::RoomData{ 2, "Room 2", "Lots", 2, 56, 1 });
Using jsoncons to convert to JSON and back:
#include <iostream>
#include <jsoncons/json.hpp>
namespace jc = jsoncons;
// Declare the traits. Specify which data members need to be serialized.
JSONCONS_ALL_MEMBER_TRAITS(ns::RoomData, id, name, maxPlayers,
questionCount, timePerQuestion, isActive);
int main()
{
std::vector<ns::RoomData> rooms;
rooms.push_back(ns::RoomData{ 1, "Room 1", "Few", 2, 56, 1 });
rooms.push_back(ns::RoomData{ 2, "Room 2", "Lots", 2, 56, 1 });
std::string s;
jc::encode_json(rooms, s, jc::indenting::indent);
std::cout << "(1)\n" << s << "\n\n";
auto rooms2 = jc::decode_json<std::vector<ns::RoomData>>(s);
std::cout << "(2)\n";
for (auto item : rooms2)
{
std::cout << "id: " << item.id << ", name: " << item.name
<< ", maxPlayers: " << item.maxPlayers << "\n";
}
}
Output:
(1)
[
{
"id": 1,
"isActive": 1,
"maxPlayers": "Few",
"name": "Room 1",
"questionCount": 2,
"timePerQuestion": 56
},
{
"id": 2,
"isActive": 1,
"maxPlayers": "Lots",
"name": "Room 2",
"questionCount": 2,
"timePerQuestion": 56
}
]
(2)
id: 1, name: Room 1, maxPlayers: Few
id: 2, name: Room 2, maxPlayers: Lots
Using nlohmann to convert to JSON and back:
#include <iostream>
#include <iomanip>
#include <nlohmann/json.hpp>
namespace nh = nlohmann;
// Provide from_json and to_json functions in the same namespace as your type
namespace ns {
void from_json(const nh::json& j, ns::RoomData& val)
{
j.at("id").get_to(val.id);
j.at("name").get_to(val.name);
j.at("maxPlayers").get_to(val.maxPlayers);
j.at("questionCount").get_to(val.questionCount);
j.at("timePerQuestion").get_to(val.timePerQuestion);
j.at("isActive").get_to(val.isActive);
}
void to_json(nh::json& j, const ns::RoomData& val)
{
j["id"] = val.id;
j["name"] = val.name;
j["maxPlayers"] = val.maxPlayers;
j["questionCount"] = val.questionCount;
j["timePerQuestion"] = val.timePerQuestion;
j["isActive"] = val.isActive;
}
} // namespace ns
int main()
{
std::vector<ns::RoomData> rooms;
rooms.push_back(ns::RoomData{ 1, "Room 1", "Few", 2, 56, 1 });
rooms.push_back(ns::RoomData{ 2, "Room 2", "Lots", 2, 56, 1 });
std::stringstream ss;
nh::json j = rooms;
ss << std::setw(4) << j;
std::cout << "(1)\n" << ss.str() << "\n\n";
nh::json j2 = nh::json::parse(ss.str());
auto rooms2 = j2.get<std::vector<ns::RoomData>>();
std::cout << "(2)\n";
for (auto item : rooms2)
{
std::cout << "id: " << item.id << ", name: " << item.name
<< ", maxPlayers: " << item.maxPlayers << "\n";
}
}
Output:
(1)
[
{
"id": 1,
"isActive": 1,
"maxPlayers": "Few",
"name": "Room 1",
"questionCount": 2,
"timePerQuestion": 56
},
{
"id": 2,
"isActive": 1,
"maxPlayers": "Lots",
"name": "Room 2",
"questionCount": 2,
"timePerQuestion": 56
}
]
(2)
id: 1, name: Room 1, maxPlayers: Few
id: 2, name: Room 2, maxPlayers: Lots
Personally I like ThorsSerializer.
Serializing data is then trivial:
#include "ThorSerialize/JsonThor.h"
#include "ThorSerialize/SerUtil.h"
#include <iostream>
#include <string>
struct RoomData
{
unsigned int id;
std::string name;
std::string maxPlayers;
unsigned int questionCount;
unsigned int timePerQuestion;
unsigned int isActive;
};
ThorsAnvil_MakeTrait(RoomData, id, name, maxPlayers, questionCount, timePerQuestion, isActive);
Example Usage:
int main()
{
using ThorsAnvil::Serialize::jsonImport;
using ThorsAnvil::Serialize::jsonExport;
RoomData data{6, "Bed Room", "Lots of them", 2, 56, 1};
std::cout << jsonExport(data) << "\n";
}
Output:
{
"id": 6,
"name": "Bed Room",
"maxPlayers": "Lots of them",
"questionCount": 2,
"timePerQuestion": 56,
"isActive": 1
}
You should use a json library. nlohmann/json is solid choice nowadays, but you can find a comparison by comformance and performance here.
Also you can omit the typedef in C++, it automatically creates one.
