关于fstream only reading in 1 structure的问题

Question

我有以下问题:我的使用fstream的程序似乎不能在我的.dat文件中写入超过1个数据struct。

下面是我的代码，我只能添加一组数据。当我尝试添加另一个时，它起作用了，但没有写出来。知道为什么吗？

例如，我运行此函数，键入详细信息，然后成功地输入了一组预订信息，信息存储在我的.dat文件中。

当我重新运行此功能时，键入详细信息，第二组预订信息没有记录在我的.dat文件中。因此，我的.dat文件最终只有第一个条目，没有存储后续条目

void booking::bkForm(fstream& afile, bForm& b)
{
    customer c;
    GM g;
    GM::holidayPackages h;
    char fname [30];
    char lname [30];
    char address [50];
    char date [30];
    char req [100];
    int pid, position, choice;
    bool iStat = false;
    bool dStat = false;
    int noOfRecords = getNoBFRecords(afile);
    int q = g.getNoOfHRecords(afile);
    cout << "Please Fill Up Required Booking Form." << endl;
    cout << "Please enter your first name: ";
    cin.clear();
    cin.ignore(100, '\n');
    cin.getline(fname, 30);
    cout << "Please enter your last name: ";
    cin.getline(lname,30);
    cout << "Please enter your address: ";
    cin.getline(address,50);

    cout << "\nThese are the available Packages to choose from." << endl;
    g.printHolidayPackages(afile, h);
    afile.open("holidayPackages.dat", ios::in | ios::binary);
    while(iStat == false)
    {
        cout << "\nPlease enter the Package ID of the tour that you want to join." << endl;
        cout << "Package ID: ";
        cin >> pid;
        for(int i = 0; i < q; i++)
        {
                afile.read (reinterpret_cast <char *>(&h), sizeof(h));
                if(pid == h.holID)
                {
                    iStat = true;
                    position = i;
                }
        }
        if(iStat == false)
        {
            cout << "ID not found, please enter valid Package ID" << endl;
        }
    }

    while(choice!=1 && choice!=2)
    {
        afile.seekg ((position) * sizeof (GM::holidayPackages), ios::beg);
        afile.read (reinterpret_cast <char *>(&h), sizeof (h));
        cout << "\nPleasse choose the Date of tour that you want to join." << endl;
        cout << "1) " << h.holDate1 << endl;
        cout << "2) " << h.holDate2 << endl;
        cout << "Your choice: ";
        cin >> choice;
        if(choice == 1)
        {
            strcpy(date, h.holDate1);
        }
        else
        {
            strcpy(date, h.holDate2);
        }
    }

    cout << "\nPlease State Any Special Requirement That You Have Below." << endl;
    cin.clear();
    cin.ignore(100, '\n');
    cin.getline(req, 100);

    afile.close();

    afile.open("bookingInfo.dat", ios::out | ios::app | ios::binary);

    strcpy(b.bfName, fname);
    strcpy(b.blName, lname);
    strcpy(b.bAddress, address);
    strcpy(b.bDate, date);
    strcpy(b.bStatus, "Unchecked");
    strcpy(b.bReq, req);
    b.packageID = pid;

    srand(time(NULL));
    int a = rand () % 100000+899990; // random 6 digit number as booking ref.
    for(int k = 0; k < noOfRecords; k++)
    {
        afile.read (reinterpret_cast <char *>(&b), sizeof(b));
        while(a == b.bookingRef)
        {
                a = rand () % 100000+899990;
        }

    }
    b.bookingRef = a;

    cout << "Booking Submitted."  << endl;
    cout << "Please take down the booking reference no : " << b.bookingRef << endl;
    cout << "You will need the reference number to check the status of your booking" << endl;

    afile.write(reinterpret_cast <const char *>(&b), sizeof(b));
    afile.close();

}

这是一些示例输出。只有一个结果，而不是几个。

==========================================================
Details Of Booking Number: 0
===========================================================
Booking Reference no: 966373
Customer Name: Cheryl Tan
Customer Address: St24 Tampines
Package ID of Package Booked: 9102
Package Date Choosen: 02032014
Special Requirements: none
Booking Status: Unchecked

Answer 1

没关系，我意识到我错了。

错误是我调用了读，但我只打开了写/追加的文件。

更正后的代码片段将如下所示。

afile.open("bookingInfo.dat", ios::in | ios::binary); //changed here to read
    srand(time(NULL));
    int a = rand () % 100000+899990; // random 6 digit number as booking ref.
    for(int k = 0; k < noOfRecords; k++)
    {
        afile.read (reinterpret_cast <char *>(&b), sizeof(b));
        while(a == b.bookingRef)
        {
                a = rand () % 100000+899990;
        }

    }
    afile.close(); // close read

    afile.open("bookingInfo.dat", ios::out | ios::app | ios::binary); // open append
    strcpy(b.bfName, fname);
    strcpy(b.blName, lname);
    strcpy(b.bAddress, address);
    strcpy(b.bDate, date);
    strcpy(b.bStatus, "Unchecked");
    strcpy(b.bReq, req);
    b.packageID = pid;
    b.bookingRef = a;

    cout << "Booking Submitted."  << endl;
    cout << "Please take down the booking reference no : " << b.bookingRef << endl;
    cout << "You will need the reference number to check the status of your booking" << endl;

    afile.write(reinterpret_cast <const char *>(&b), sizeof(b));
    afile.close(); // close append