如何覆盖子类中的抽象类构造函数

Question

我刚从java转到c ++，我真的很挣扎曾经的基本概念。我想做的就是创建一个名为'Spaceship'的抽象类，给它一个带有4个参数的构造函数，然后在一个名为'Alienspaceship'的子类中，我想创建一个带有5个参数但继承'太空飞船'的构造函数'构造者前4个论点。我一直在寻找这个地方，似乎无法找到我正在寻找的东西。以下是我的代码。请感谢能帮助我的人！

头

#ifndef SPACESHIP
#define SPACESHIP

#include "Enum.h"

class Spaceship{
    public:
    float health;
    float food;
    float cash;
    float misc;

public:
    Spaceship(float, float, float, float);

};

class AlienSpaceship: public Spaceship{
    OrganismType race;

    public:
        AlienSpaceship(float, float, float, float, OrganismType):Spaceship(float, float, float, float){}
};

#endif

CPP

#include "Spaceship.h"

Spaceship::Spaceship(float health, float food, float cash, float misc){
    this->health = health;
    this->food = food;
    this->cash = cash;
    this->misc = misc;
}

AlienSpaceship::AlienSpaceship(float health, float food, float cash, float misc, OrganismType race):Spaceship(health, food, cash, misc){
    this->race = race;
}

Answer 1

您似乎误解了构造函数初始化列表的工作原理。

它用在构造函数的定义（即实现）中，构造函数的声明不需要它。

事实上，你在AlienSpaceship类中的当前声明实际上定义（实现）构造函数，因为结束{}。

因此，对于课程，您需要做的就是

class AlienSpaceship: public Spaceship{
    ...
    public:
        AlienSpaceship(float, float, float, float, OrganismType);
};

---

在相关的说明中，我建议您使用初始化列表来初始化成员变量，然后您的构造函数可能只是

Spaceship::Spaceship(float health, float food, float cash, float misc)
    : health(health), food(food), cash(cash), misc(misc)
{ /* Empty */ }

AlienSpaceship::AlienSpaceship(float health, float food, float cash, float misc, OrganismType race)
    : Spaceship(health, food, cash, misc), race(race)
{ /* Empty */ }

当然，这可以在类定义本身在线完成：

class AlienSpaceship: public Spaceship{
    ...
    public:
        AlienSpaceship(float health, float food, float cash, float misc, OrganismType race)
            : Spaceship(health, food, cash, misc), race(race)
        { /* Empty */ }
};

Answer 2

AlienSpaceship(float, float, float, float, OrganismType):Spaceship(float, float, float, float){}

应该只是：

AlienSpaceship(float, float, float, float, OrganismType);

在你的标题中。您实际上已在标题中创建了第二个实现...

Answer 3

你应该只有每个类成员的一个定义，但你有两个

第一个（隐含在类定义中）

public:
AlienSpaceship(float, float, float, float, OrganismType):Spaceship(float, float, float, float)
{}

第二个在源文件

AlienSpaceship::AlienSpaceship(float health, float food, float cash, float misc, OrganismType race):Spaceship(health, food, cash, misc)
{
    this->race = race;
}

选择其中之一，或者说

AlienSpaceship(float health, float food, float cash, float misc, OrganismType race):Spaceship(health, food, cash, misc)
{
    this->race = race;
}

进入类定义

要么在课堂上宣布

class AlienSpaceship: public Spaceship{
OrganismType race;

public:
AlienSpaceship(float, float, float, float, OrganismType);

并在源文件中定义

AlienSpaceship::AlienSpaceship(float health, float food, float cash, float misc, OrganismType race):Spaceship(health, food, cash, misc)
{
    this->race = race;
}

还有，像这样的声明

AlienSpaceship(float, float, float, float, OrganismType):Spaceship(float, float, float, float)

is incorrect too. Actually, it conatains a part of defenition.