指针传染媒介。 BOOST序列化

Question

我想使用BOOST序列化/反序列化以下向量中对象的值（而不是指针）：

std :: vector <A*> m_vector; 

要序列化我使用以下代码：

int nItems = m_vector.size();
ar & nItems;
std::for_each(m_vector.begin(), m_vector.end(), [&ar](A* pItem) {
    ar & *pItem;
});

并反序列化：

int nItems;
ar & nItems;
for (int i = 0; i < nItems; ++i) {
    A* pItem;
    ar & *pItem;  ///////////// Run-Time Check Failure #3
    m_vector.push_back(pItem);
}

但是当我运行程序时，我收到以下错误：

Run-Time Check Failure # 3 - The variable 'pItem' is Being Used without Being initialized. 

我究竟做错了什么？

谢谢。

Answer 1

您需要为pItem指向的对象分配内存：

A* pItem = new A;
ar & *pItem;
m_vector.push_back(pItem);

错误是因为虽然你有一个指针，但指针指向的内存位置没有对象 - 指针的值是垃圾（未初始化的指针）。

当不再需要向量中指针指向的对象时，不要忘记调用delete以防止内存泄漏。 更好的是，使用智能指针（例如boost::shared_ptr<> ）来确保在不再可访问时释放内存。

Answer 2

2年后，但值得一提。

有一个更好的解决方案来序列化指向对象或任何其他STL容器（列表，集等）的指针向量。 要序列化矢量，请添加：

#include <boost/serialization/vector.hpp>

然后你需要实现serialize（）方法并用archieve与你的朋友交往。 在这个例子中解释了一切（仔细阅读所有评论，它们非常重要）：

#include <fstream>
#include <iostream>
#include <vector>
#include <iostream>

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


class Abc{
    // In order to make Abc serializable
    // you need to friend this lass with serialization::access
    friend class boost::serialization::access;

    // and then add this method
    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    {
        // choose what class fields do you want to serialize
        ar & a;
        ar & b;
        ar & c;
    }
public:
    int a;
    int b;
    int c;

    // don't forget about default constructor! It's necessary for serialization!
    Abc(){};
    Abc(int a, int b, int c): a(a), b(b), c(c){};
};

class GpsPosition
{
private:
    // as mentioned above...
    friend class boost::serialization::access;
    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    {
        ar & degrees;
        ar & minutes;
        ar & seconds;
        ar & wektorIntow;
    }
    int degrees;
    int minutes;
    float seconds;
public:
    std::vector<Abc*> abcVector;
    GpsPosition(){};
    GpsPosition(int d, int m, float s): degrees(d), minutes(m), seconds(s)
    {
        // adding some objects to abcVector
        abcVector.push_back(new Abc(1, 2, 3));
        abcVector.push_back(new Abc(3, 2, 3));
        abcVector.push_back(new Abc(2, 2, 3));
        abcVector.push_back(new Abc(1, 2, 3));
    }
    int getDegrees(){ return this->degrees; }
    int getMinutes(){ return this->minutes; }
    float getSeconds(){ return this->seconds; }
};

int main(){

    // And now how to use it

    // Saving to file:
    std::ofstream fileHandler("filename");
    const GpsPosition position1(35, 59, 24.567f);
    {
        boost::archive::text_oarchive boostOutputArchieve(fileHandler);
        boostOutputArchieve << position1;
    }

    // Reading from file:
    GpsPosition newPosition;
    {
        std::ifstream fileHandler;
        try{
            fileHandler.open("filenacme");
            boost::archive::text_iarchive boostInputArchieve(fileHandler);
            // read class state from archive
            boostInputArchieve >> newPosition;
            // archive and stream closed when destructors are called
            fileHandler.close();
            }
        catch (std::ifstream::failure e) {
            std::cerr << "Exception opening/reading/closing file";
        }
        catch(boost::archive::archive_exception e){
            std::cerr << "Exception opening/reading/closing file";
        }
    }

    // print to the console
    std::cout << newPosition.getMinutes() << std::endl; 
    std::cout << newPosition.abcVector[0]->a;
    std::cin.get();

    return 0;
}

有关更多信息，请查看本教程： http ： //www.boost.org/doc/libs/1_55_0/libs/serialization/doc/index.html