Boost 序列化 IO 错误答案

【问题标题】：Boost Serialization IO errorBoost 序列化 IO 错误
【发布时间】：2013-01-23 13:42:51
【问题描述】：

在下面的代码中，我尝试将两个对象写入一个没有扩展名的文件。问题最初出现在写入阶段，因为实际上没有任何内容写入文件。然后是第二部分；读取阶段，使用以下行打开文件时会导致异常：

boost::archive::text_iarchive ia(ifs);

我从 boost 示例 1 中获取了这个。我还尝试在此页面上关注此问题的第三个答案Boost Serialization multiple objects

    #include <fstream>

// include headers that implement a archive in simple text format
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
/////////////////////////////////////////////////////////////
// gps coordinate
//
// illustrates serialization for a simple type
//
class gps_position
{
    private:
        friend class boost::serialization::access;
    // When the class Archive corresponds to an output archive, the
    // & operator is defined similar to <<.  Likewise, when the class Archive
    // is a type of input archive the & operator is defined similar to >>.
        template<class Archive>
        void serialize(Archive & ar, const unsigned int version)
        {
            ar & degrees;
            ar & minutes;
            ar & seconds;
        }
        int degrees;
        int minutes;
        float seconds;
    public:
        gps_position(){};
        gps_position(int d, int m, float s) :
        degrees(d), minutes(m), seconds(s)
    {}
};
int main()
{
    // create and open a character archive for output
    std::ofstream ofs("filename",std::ios::app);

    // create class instance

    gps_position g0(35, 59, 24.567f);
    gps_position g1(35, 59, 88.567f);
    // save data to archive
    //{
        boost::archive::text_oarchive oa(ofs);
        // write class instance to archive
        size_t number_of_objects = 2;
        oa << number_of_objects;
        oa << g0;
        oa << g1;
        // archive and stream closed when destructors are called
   // }

    // ... some time later restore the class instance to its orginal state

    gps_position newg0;
    gps_position newg1;
   // {
        // create and open an archive for input
        std::ifstream ifs("filename");
        boost::archive::text_iarchive ia(ifs);
        // read class state from archive


        ia >> number_of_objects;
        ia >> newg0;
        ia >> newg1;
        // archive and stream closed when destructors are called
    //}

    return 0;
}

【问题讨论】：

我不确定，但也许您需要将std::ios::app 与std::ios::out 结合起来才能真正写入文件。
会不会像 std::ofstream ofs("filename",std::ios::app|std::ios::out); ?没试过，它崩溃了！
是的：std::ios::app | std::ios::out
刷新并关闭流，然后尝试读取
取消注释围绕写作阶段的大括号；否则存档和 ofstream 在尝试读取之前都不会关闭。

标签： c++ serialization boost

【解决方案1】：

取消注释围绕写作阶段的大括号；否则存档和std::ofstream 在尝试读取之前都不会关闭。

正如cmets中的几个人所说，需要刷新和关闭流，这是在销毁std::ofstream的实例时自动完成的；在那种情况下遇到写作阶段的右大括号时。

【讨论】：