双重继承中的构造函数

Question

我的构造函数有问题。我有类车辆，然后我创建了类motorVehicle，它在vehicle 之后继承，然后我想创建类motorcycle，它在motorVehicle 之后继承，我无法创建我的默认构造函数，因为我有错误： vehicle 和 motorVehicle 类没有被我更改，motorcycle 类在 2 个选项中，这些选项都不起作用，但我给你两个选项。顺便说一句，问题是（第一个选项）：没有匹配的构造函数用于初始化“motorVehicle”并且需要第二个选项；在表达式和预期的成员名称之后或；在声明说明符之后

class vehicle {
public:
    int numberOfWheels;
    string color;
    float vehiclePayload;

    vehicle(): numberOfWheels{4},color{"black"},vehiclePayload{500}{

    }
};
class motorVehicle : public vehicle {
public:
    float tankCapacity;
        float fuelConsumption;
        float mileage;
        float currentAmountOfFuel;
        int yearOfProduction;
        unsigned long long int vin;
        motorVehicle(): tankCapacity{30}, fuelConsumption{6}, mileage{100}, currentAmountOfFuel{10}, yearOfProduction{2021}, vin{1}, vehicle{4, "black", 500} {

        }
};


class motorcycle : public motorVehicle{
public:
    float bootSize;
    string brand;
    string model;
    motorcycle(): bootSize{500}, brand{"Ninja"}, model{"Kawasaki"}, motorVehicle{30,6,100,10,2021,1,vehicle{4, "black", 500}}{

    }

};

class motorcycle : public motorVehicle{
public:
    float bootSize;
    string brand;
    string model;
    motorcycle(): bootSize{500}, brand{"Ninja"}, model{"Kawasaki"}, motorVehicle(){30,6,100,10,2021,1,vehicle{4, "black", 500}}{

    }

};

Answer 1

您的基类没有声明任何采用实际值的构造函数。由于这些类确实声明了一个默认构造函数，聚合初始化不起作用：有一个声明的构造函数，即该类不是聚合。但是，如果您想直接初始化基类，可以使用它们的隐式生成复制构造函数。但是，您仍然需要单独填充类的内容，因为您需要使用默认构造函数创建对象：

class motorVehicle : public vehicle {
public:
    float tankCapacity;
    float fuelConsumption;
    float mileage;
    float currentAmountOfFuel;
    int yearOfProduction;
    unsigned long long int vin;
    motorVehicle(): tankCapacity{30}, fuelConsumption{6}, mileage{100}, currentAmountOfFuel{10}, yearOfProduction{2021}, vin{1},
        vehicle([]{
            vehicle rc;
            rc.numberOfWheels = 4;
            rc.color = "black";
            rc vehiclePayload = 500;
            return rc;
            }()) {

    }
 };

显然，您可以使用因子函数而不是使用 lambda 函数，假设 makeVehicle(int wheels, std::string const& color, float payload) 适当地初始化成员。不过，vehicle 确实应该有一个合适的构造函数。