C++ 从文件错误中读取对象 [英] C++ Reading Objects from File Error

问题描述

        fstream file;
        Patient Obj("XXX",'M',"XXX");
        file.open("Patients.dat",ios::in|ios::out|ios::app);
        file.seekg(ios::end);
        file.write((char*)&Obj,sizeof(Obj));
        file.seekg(ios::beg);


        Patient x;

        file.read((char*)&x,sizeof(x));
        x.printallInfo();

        file.close();

我正在使用此代码将对象写入文件，但是当我读取数据时 VC++ 6 崩溃并抛出异常访问冲突".(写入成功)

I'm writing objects to files using this code but when i reading data VC++ 6 Crashes and thows a exception 'Access violation' .(Writing is successful)

完整代码

#include <iostream>
#include<fstream>
#include <iomanip.h>


#include "Patient.cpp"

using namespace std;

int main(){




            fstream file;
            Patient Obj("XXX",'M',"XXX");
            file.open("Patients.dat",ios::in|ios::out|ios::app);
            file.seekg(ios::end);
            file.write((char*)&Obj,sizeof(Obj));
            file.seekg(ios::beg);


            Patient x;

            file.read((char*)&x,sizeof(x));

            file.close();


    return 0;


}

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推荐答案

这似乎是一种编组类的脆弱且不可移植的方式.您这样做的方式可能会发生的一件事是，您没有对正在序列化的数据进行深层复制.例如，如果您的 Patient 类的成员之一是 std::string，则会将裸指针写入文件，但不会写入字符串数据.更糟糕的是，当你读回它时，指针指向......某处......

That seems like a brittle and non-portable way to marshal classes. One thing that could be happening with the way you do this is that you aren't making a deep copy of the data you're serializing. for instance, if one of the members of your Patient class is a std::string, a bare pointer is written to the file, but no string data is written. Worse, when you read that back in, the pointer points... somewhere...

处理这个问题的更好方法是实际实现一个特定于类的方法，该方法确切地知道如何序列化和反序列化每个成员.

A better way to deal with this issue is to actually implement a class specific method that knows exactly how to serialize and unserialize each member.

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