如何使用boost序列化轻松序列化包含另一个自定义类的STL容器的自定义类？

Question

我已经阅读了这里的教程http://www.boost.org/doc/libs/1_59_0/libs/serialization/doc/index.html 并搜索了很多页面，但我仍然不知道该怎么做。

我已经阅读了如何序列化自定义类以及如何序列化包含 std::string 或指针的 STL 容器的自定义类。但是我不确定如何使用boost序列化轻松序列化包含另一个自定义类的STL容器的自定义类？由于 std::string 和指针是标准的 C++ 类型，boost 知道如何处理它们。如果是自定义类的 STL 容器，我觉得我必须告诉 boost 在序列化时如何处理它。但是怎么做？这是我自定义的2个类。

class Instance
{
public:
    Instance(){}
    ~Instance();
    //... a lot of functions here.
private:
    InstanceIdentity identity_;
    mutable ClassLabel class_label_;
    mutable FeatureGroup features_;
    friend class InstanceManager;
};

class InstanceManager
{
public:
    InstanceManager(){}
    ~InstanceManager();
    // a lot of functions here.
private:
    set<Instance> instances_;
};

根据http://www.boost.org/doc/libs/1_59_0/libs/serialization/doc/index.html的教程部分，由于boost知道如何处理STL容器，所以我需要做的是添加

friend class boost::serialization::access;
template<class Archive>
void serialize(Archive & ar, const unsigned int version)
{
    ar & instances_;
}

在类 InstanceManager 中。并添加

friend class boost::serialization::access;
template<class Archive>
void serialize(Archive & ar, const unsigned int version)
{
    // A lot of things like the following example.
    //ar & degrees;
    //ar & minutes;
    //ar & seconds;
}

在类实例中。那正确吗？或者有更好的方法。通过编码来测试这一点需要很多时间。那么，谁能告诉我答案？

Answer 1

答案是肯定的。这是一个完整的工作示例。我发明了一些简单的类型：

struct InstanceIdentity { int id;            };
struct ClassLabel       { std::string value; };
struct FeatureGroup     { size_t count;      };

使用非侵入式序列化：

namespace boost { namespace serialization {
    template <typename Ar>
        void serialize(Ar& ar, InstanceIdentity& ii, unsigned) { ar & ii.id; }
    template <typename Ar>
        void serialize(Ar& ar, ClassLabel& cl, unsigned) { ar & cl.value; }
    template <typename Ar>
        void serialize(Ar& ar, FeatureGroup& fg, unsigned) { ar & fg.count; }
} }

Instance 和 InstanceManager 类将它们的序列化方法作为成员（由于私有成员）：

template <typename Ar>
    void Instance::serialize(Ar& ar, unsigned) { ar & identity_ & class_label_ & features_; }

template <typename Ar>
    void InstanceManager::serialize(Ar& ar, unsigned) { ar & instances_; }

Live On Coliru

#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/serialization/set.hpp>
#include <boost/serialization/serialization.hpp>
#include <boost/serialization/access.hpp>

struct InstanceIdentity { int id;            };
struct ClassLabel       { std::string value; };
struct FeatureGroup     { size_t count;      };

class Instance
{
public:
    Instance(){}
    ~Instance() = default;
    //... a lot of functions here.

    bool operator<(Instance const& other) const {
        return identity_.id < other.identity_.id;
    }
private:
    InstanceIdentity identity_;
    mutable ClassLabel class_label_;
    mutable FeatureGroup features_;
    friend class InstanceManager;

    friend class boost::serialization::access;
    template <typename Ar>
        void serialize(Ar& ar, unsigned) { ar & identity_ & class_label_ & features_; }
};

class InstanceManager
{
public:
    InstanceManager()
    {
        Instance a, b, c;

        a.class_label_.value = "label a";
        b.class_label_.value = "label b";
        c.class_label_.value = "label c";

        a.features_.count = 42;
        b.features_.count = 24;
        c.features_.count = -9;

        a.identity_.id = rand();
        b.identity_.id = rand();
        c.identity_.id = rand();

        instances_.insert(instances_.end(), a);
        instances_.insert(instances_.end(), b);
        instances_.insert(instances_.end(), c);
    }

    ~InstanceManager() = default;
    // a lot of functions here.
private:
    std::set<Instance> instances_;

    friend class boost::serialization::access;
    template <typename Ar>
        void serialize(Ar& ar, unsigned) { ar & instances_; }
};

namespace boost { namespace serialization {
    template <typename Ar>
        void serialize(Ar& ar, InstanceIdentity& ii, unsigned) { ar & ii.id; }
    template <typename Ar>
        void serialize(Ar& ar, ClassLabel& cl, unsigned) { ar & cl.value; }
    template <typename Ar>
        void serialize(Ar& ar, FeatureGroup& fg, unsigned) { ar & fg.count; }
} }

int main() {

    InstanceManager im;

    boost::archive::text_oarchive oa(std::cout);
    oa << im;

}

打印

22 serialization::archive 12 0 0 0 0 3 0 0 0 0 0 846930886 0 0 7 label b 0 0 24 1681692777 7 label c 18446744073709551607 1804289383 7 label a 42