c++ - boost 序列化 : Does the default constructor have to be public?

Question

只是一点点信息，似乎在任何地方都没有记录。有人知道吗？因为我想将其设为私有(private)，希望从声明为友元的 boost::serialization::access 调用构造函数。

Answer 1

测试示例。鉴于这是有效的，我假设它是一个功能，如果 future 的版本不允许访问授权机制向私有(private)默认构造函数授予访问权限，我会感到不安。

#include <boost/serialization/access.hpp>
#include <boost/serialization/shared_ptr.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/archive/text_oarchive.hpp>
#include <sstream>
#include <iostream>

struct Colour {
    double colour[4];
    boost::shared_ptr<Colour> alt;
    static boost::shared_ptr<Colour> test() {
       return boost::shared_ptr<Colour>(new Colour);
    }
private:
    friend class boost::serialization::access;

    template<class Archive>
    void serialize(Archive & ar, const unsigned int /*file_version*/) {
        ar & colour;
    }

    Colour() {
        std::cout << "Getting called" << std::endl;
    }
};

int main() {
    boost::shared_ptr<Colour> c = Colour::test();
    c->alt = Colour::test();

    std::cout << "Created" << std::endl;

    std::stringstream str;
    boost::archive::text_oarchive oa(str);
    oa & c;

    std::cout << "Saved" << std::endl;

    c.reset();

    boost::archive::text_iarchive ia(str);
    ia & c;

    std::cout << "Restored" << std::endl;
}

(有趣的是，它似乎默认构造一个然后在我的系统上复制构造另一个)。