对指针向量进行排序一次，然后崩溃并"unable to read memory"

Question

我有一个向量Flight pointers，我将其传递到一个函数中，以便在屏幕上进行排序和显示。我在Flight class中使用一个函子来进行排序。它第一次工作得很好，然后在sortCredential增加后，当它第二次尝试遍历飞行矢量时崩溃。我得到的错误是Access violation reading location 0x013DFFFC，所以我打赌这与第一次排序后失去对向量内存位置的跟踪有关。提前感谢您提供的任何帮助。这是我的排序功能：

//this function displays the flight schedule and sorts it by any field
void showFlightSchedule(vector<Flight*>& flights)
{
    //declare local variables
    char choice = ' ';
    int sortCriteria = 1;
while (toupper(choice) != 'X')
{
    //choosing which field to sort the schedule by
    switch (sortCriteria)
    {
    case 1:
        sort (flights.begin(), flights.end(), Flight::SortByDepartCity);
        break;
    case 2:
        sort (flights.begin(), flights.end(), Flight::SortByDestinationCity);
        break;
    case 3:
        sort (flights.begin(), flights.end(), Flight::SortByDepartTime);
        break;
    case 4:
        sort (flights.begin(), flights.end(), Flight::SortByArrivalTime);
        break;
    case 5:
        sort (flights.begin(), flights.end(), Flight::SortByFlightNumber);
        break;
    case 6:
        sort (flights.begin(), flights.end(), Flight::SortByAircraftType);
        break;
    case 7:
        sort (flights.begin(), flights.end(), Flight::SortByFreqFlyPoints);
        break;
    case 8:
        sort (flights.begin(), flights.end(), Flight::SortByFlightFull);
        break;
    }

    //display header
    system("cls");
    cout << left << endl;
    cout << "     " << setw(7) << "From" << setw(6) << "To" << setw(8) << "Depart" << setw(8) << "Arrive" <<
        setw(8) << "Flight" << setw(12) << "Aircraft" << setw(12) << "Frequent" << setw(6) << "Flightn";
    cout << "tttt  " << setw(10) << "Number" << setw(8) << "Type" << setw(14) << "Flyer Points" << setw(6) << "Statusn";
    //slightly altering the header to indicate how the list is sorted
    switch (sortCriteria)
    {
    case 1:
        cout << "   --\_/------------------------------------------------------------------nn";
        break;
    case 2:
        cout << "   ---------\_/-----------------------------------------------------------nn";
        break;
    case 3:
        cout << "   ----------------\_/----------------------------------------------------nn";
        break;
    case 4:
        cout << "   ------------------------\_/--------------------------------------------nn";
        break;
    case 5:
        cout << "   --------------------------------\_/------------------------------------nn";
        break;
    case 6:
        cout << "   -----------------------------------------\_/---------------------------nn";
        break;
    case 7:
        cout << "   -----------------------------------------------------\_/---------------nn";
        break;
    case 8:
        cout << "   ----------------------------------------------------------------\_/----nn";
        break;
    }
    //step through the flights vector displaying the information
    for (int idx = 0; idx < flights.size(); idx++)
    {
        cout << "     " << setw(7) << flights[idx]->getDepartCity() << setw(6) << flights[idx]->getDestinationCity() << setw(8) <<
            flights[idx]->getDepartTime() << setw(9) << flights[idx]->getArrivalTime() << setw(10) << flights[idx]->getFlightNumber() << setw(11) <<
            flights[idx]->getAircraftType() << setw(11) << flights[idx]->getFreqFlyPoints();
        if (flights[idx]->getFlightFull())
            cout << setw(6) << "FULLnn";
        else
            cout << endl << endl;
        flights[idx]++;
    }
    //display footer
    cout << "   -----------------------------------------------------------------------nn";
    cout << "ttt  C -- Change Sortingn";
    cout << "ttt  X -- Exit to Main Menun";
    cout << "ttt  Enter C or X: ";
    //get choice from user
    cin >> choice;
    //error-trapping loop
    while ((toupper(choice) != 'C') && (toupper(choice) != 'X'))
    {
        cout << "Please choose "C" or "X": ";
        cin >> choice;
    }
    //changing the sort flag
    if (sortCriteria == 8)
        sortCriteria = 1;
    else
        sortCriteria++;     
}
}

在我的Flight.h文件中，我有以下排序语句：

static bool SortByDepartCity(const Flight* f1, const Flight* f2)
{
    return f1->departCity < f2->departCity;
}
static bool SortByDestinationCity(const Flight* f1, const Flight* f2)
{
    return f1->destinationCity < f2->destinationCity;
}
static bool SortByDepartTime(const Flight* f1, const Flight* f2)
{
    return f1->departTime < f2->departTime;
}
static bool SortByArrivalTime(const Flight* f1, const Flight* f2)
{
    return f1->arrivalTime < f2->arrivalTime;
}
static bool SortByFlightNumber(const Flight* f1, const Flight* f2)
{
    return atoi(f1->flightNumber.c_str()) < atoi(f2->flightNumber.c_str());
}
static bool SortByAircraftType(const Flight* f1, const Flight* f2)
{
    return f1->aircraftType < f2->aircraftType;
}
static bool SortByFreqFlyPoints(const Flight* f1, const Flight* f2)
{
    return f1->freqFlyPoints > f2->freqFlyPoints;
}
static bool SortByFlightFull(const Flight* f1, const Flight* f2)
{
    return f1->flightFull < f2->flightFull;
}

Answer 1

删除此

航班[idx]++；

在打印循环的最后一行。

附言：这里有一些简化的代码

template< class T, class FieldType, FieldType T::*FieldPtr >
struct LessBy {
    bool operator()( const T * left, const T * right ) const {
        return left->*FieldPtr < right->*FieldPtr;
    }
};
typedef LessBy< Flight, std::string, & Flight::departCity > SortByDepartCity;
typedef LessBy< Flight, std::string, & Flight::destinationCity > SortByDestinationCity;
//and so on

Answer 2

打印时执行的此行：

flights[idx]++;

将修改每个指针，几乎可以肯定地使每个指针对取消引用无效
你应该删除它。（它看起来像是旧代码留下的一行。）

将排序与打印分离也是一个好主意，因为没有人期望输出函数修改正在打印的数据。

和除非你有充分的理由，否则你不应该使用航班指针。