c++ - 尝试学习指针时练习程序崩溃

Question

我仍在掌握指针的过程中，为此我编写了一个快速但毫无意义的程序来练习查找指针错误。我对为什么这个示例代码崩溃感到困惑:

#include <iostream>

class VehiclePart
{
public:
    VehiclePart(int);

    int GetVehiclePartNumber();
private:
    int partNumber;
};

VehiclePart::VehiclePart(int VehiclePartNumber)
{
    partNumber = VehiclePartNumber;
}

int VehiclePart::GetVehiclePartNumber()
{
    return partNumber;
}

class Vehicle
{
public:
    Vehicle(VehiclePart* VehiclePart, int VehiclePartNumber);

    int GetVehiclePartNumber();

private:
    VehiclePart* vehiclePart;

};

Vehicle::Vehicle(VehiclePart* vehiclePart, int VehiclePartNumber)
{
    vehiclePart = new VehiclePart(VehiclePartNumber);
}

int Vehicle::GetVehiclePartNumber()
{
    return vehiclePart->GetVehiclePartNumber();
}

int main()
{
    VehiclePart* hood = nullptr;
    Vehicle car(hood, 6);

    std::cout << "Hello" << std::endl;

    std::cout << car.GetVehiclePartNumber();

    return 0;
}

我知道有更好的方法来处理事情，就像我说的那样，这只是我习惯指针以及为什么会发生崩溃的练习。感谢您的帮助。

Answer 1

Vehicle::Vehicle(VehiclePart* vehiclePart, int VehiclePartNumber)
{

请注意，您的构造函数有一个名为 vehiclePart 的参数。因此，

    vehiclePart = new VehiclePart(VehiclePartNumber);

这最终将构造函数的参数设置为 newed 类实例，而不是同名的类成员。

这与指针无关，但与作用域有关。