I want to serialize private member variables of my Player class using cereal. How can I accomplish this?

Question

Ryan McCombe · Accepted Answer

To serialize private member variables of your Player class using cereal, you can follow these steps:

Step 1: Include the necessary cereal headers:

1#include <cereal/access.hpp>
2#include <cereal/types/string.hpp>

Step 2: In your Player class, make the serialization functions private and befriend cereal::access:

1class Player {
2private:
3  std::string name;
4  int level;
5  int health;
6
7  friend class cereal::access;
8
9  template<class Archive>
10  void serialize(Archive& ar) {
11    ar(name, level, health);
12  }
13};

By making the serialize function private and friending cereal::access, you grant cereal access to your class's private members for serialization purposes.

Step 3: Serialize and deserialize the Player object as usual:

1#include <cereal/archives/binary.hpp>
2#include <fstream>
3
4int main() {
5  // Serialization
6  Player player("Alice", 10, 100);
7  std::ofstream outputFile("player.dat");
8  cereal::BinaryOutputArchive outputArchive(
9    outputFile);
10  outputArchive(player);
11
12  // Deserialization
13  Player deserializedPlayer;
14  std::ifstream inputFile("player.dat");
15  cereal::BinaryInputArchive inputArchive(
16    inputFile);
17  inputArchive(deserializedPlayer);
18}

By following this approach, cereal will be able to access and serialize the private member variables of your Player class without the need to make them public or use getter/setter functions.

Note: Be cautious when serializing private members, as it can potentially break encapsulation. Only serialize data that is necessary for saving and loading the object's state.

A complete example is below:

1#include <cereal/archives/binary.hpp>
2#include <cereal/types/string.hpp>
3#include <fstream>
4#include <iostream>
5
6class Player {
7 public:
8  Player() = default;
9  Player(const std::string& name, int level,
10    int health) : name(name), level(level),
11    health(health) {}
12
13  std::string GetName() { return name; }
14  int GetLevel() { return level; }
15  int GetHealth() { return health; }
16
17 private:
18  std::string name;
19  int level;
20  int health;
21
22  friend class cereal::access;
23
24  template <class Archive>
25  void serialize(Archive& ar) {
26    ar(name, level, health);
27  }
28};
29
30int main() {
31  // Serialization
32  Player player("Alice", 10, 100);
33  {
34    std::ofstream outputFile("player.dat");
35    cereal::BinaryOutputArchive outputArchive(
36      outputFile);
37    outputArchive(player);
38  }
39
40  // Deserialization
41  Player deserializedPlayer;
42  {
43    std::ifstream inputFile("player.dat");
44    cereal::BinaryInputArchive inputArchive(
45      inputFile);
46    inputArchive(deserializedPlayer);
47  }
48
49  std::cout << "Deserialized Player:\n";
50  std::cout << "Name: "
51    << deserializedPlayer.GetName() << "\n";
52  std::cout << "Level: "
53    << deserializedPlayer.GetLevel() << "\n";
54  std::cout << "Health: "
55    << deserializedPlayer.GetHealth() << "\n";
56}

1Deserialized Player:
2Name: Alice
3Level: 10
4Health: 100

Binary Serialization using Cereal

Serializing Private Class Members with Cereal

Binary Serialization using Cereal

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