如何从继承的自定义类 C++ 中创建类型

Question

我正在尝试用 C++ 构建我的第一个游戏，我正在尝试制作一个 Inventory 系统，该系统将允许我在 Inventory 中管理和安排不同的 Item 数据类型] 容器类型。在下面的代码中，我只编写了 class 声明，但我想知道如何使我所做的 "Item" class 包含任何不同继承项的数据类型例如 Weapon、Apparel 和 Aid 类别。它会像使用 template 参数一样简单吗？如果是这样，那么我的问题是 Constructor 之类的东西如何理解在创建项目的每个实例中要做什么？ default Constructor 可能是我决定设置的基本武器之类的东西，对吗？如果有人能提供任何建议或链接，我们将不胜感激。

谢谢！

ITEM.H:

#ifndef ITEM_H
#define ITEM_H

#include <iostream>

/*************************************************
* ITEM CLASS
* *This class is the type of data to be put into
*  the Inventory Container class.
**************************************************/
class Item
{
public:

private:

};

/*************************************************
* WEAPON CLASS
* *This class is a type of Item that classifies a
*  weapon item that can be in an Inventory.
**************************************************/
class Weapon : public Item
{
public:

private:

};

/*************************************************
* APPAREL CLASS
* *This class is a type of Item that classifies an
*  apparel item that can be in an Inventory.
**************************************************/
class Apparel : public Item
{
public:

private:

};

/*************************************************
* AID CLASS
* *This class is a type of Item that classifies an
*  Aid item that can be in an Inventory.
**************************************************/
class Aid : public Item
{
public:

private:

};

#endif //ITEM_H

编辑：

这是我目前拥有的：

/*************************************************
* ITEM CLASS
* *This class is the type of data to be put into
*  the Inventory Container class.
**************************************************/
template <class T>
class Item
{
public:


private:
    T item_type;         //i.e. Weapon, Apparel, Aid, etc...

};

/*****************************************************************
* ITEM : WEAPON 
* *Below is the code for all the different Weapon classes.
******************************************************************/

/*************************************************
* WEAPON CLASS
* *This class is a type of Item that classifies a
*  weapon item that can be in an Inventory.
**************************************************/
template <class T>
class Weapon : public Item
{
public:

private:
    T weapon_type;      //i.e. Melee, Ranged, etc...
};

/*************************************************
* MELEE CLASS
* *This class is a type of Item that classifies a
*  melee item that will be used as a weapon.
**************************************************/
template <class T>
class Melee : public Weapon
{
public:

private:

};

/*************************************************
* RANGED CLASS
* *This class is a type of Item that classifies a
*  ranged item that will be used as a weapon.
**************************************************/
template <class T>
class Ranged : public Weapon
{
public:

private:

};

另一项编辑：这是最新的代码：

/*************************************************
* ITEM CLASS
* *This class is the type of data to be put into
*  the Inventory Container class.
**************************************************/
template <class T>
class Item
{
public:


protected:
    T item_type;         //i.e. Weapon, Apparel, Aid, etc...

};

/*****************************************************************
* ITEM : WEAPON 
* *Below is the code for all the different Weapon classes.
******************************************************************/

//WEAPON CLASS
template <class T>
class Weapon : public Item
{
public:

protected:
    T weapon_type;      //i.e. Melee, Ranged, etc...
};

//MELEE CLASS
template <class T>
class Melee : public Weapon
{
public:

protected:
    T melee_type;      //i.e. Blade, Blunt, Fist, etc...

};

//BLADE CLASS
template <class T>
class Blade : public Melee
{
public:

protected:
    T blade_type;      //i.e. Dagger, Sword, etc...
};

//DAGGER CLASS
template <class T>
class Dagger : public Blade
{
public:
    //Default Constructor...the only Constructor
    Dagger() : damage(1), weight(0.5) { }

    //getters
    std::string getType() const { return "Dagger"; }

protected:
    int   damage;      //amount of damage it can inflict
    float weight;      //weight of the dagger
};

Answer 1

一种解决方案是将您的类型定义为 enums.

enum ITEM_TYPE { IT_WEAPON, IT_END };
enum WEAPON_TYPE { WT_MELEE, WT_RANGED, WT_END };

class Item {
public:
    Item(ITEM_TYPE type) : item_type(type) {}
protected:
    ITEM_TYPE item_type;
};

class Weapon : public Item {
public:
    Weapon(WEAPON_TYPE type) : Item(IT_WEAPON), weapon_type(type) {}
protected:
    WEAPON_TYPE weapon_type;
};

class MeleeWeapon : public Weapon {
public:
    MeleeWeapon() : Weapon(WT_MELEE) {}
};

class RangedWeapon : public Weapon {
public:
    RangedWeapon() : Weapon(WT_RANGED) {}
};

Answer 2

您不能也不应该需要存储类型（C++ 语言意义上的类型），使用虚函数来实现您想要的。

#include <iostream>
#include <memory>
#include <vector>

class Item
{
public:
     virtual const char* type() const = 0;
};

class Weapon : public Item
{
public:
      const char* type() const override { return "Weapon"; }
};

class Ranged : public Weapon
{
public:
    const char* type() const override { return "Ranged"; }
};

class Melee : public Weapon
{
public:
    const char* type() const override { return "Melee"; }
};

class Apparel : public Item
{
public:
    const char* type() const override { return "Apparel"; }
};

int main()
{
    std::vector<std::unique_ptr<Item>> items;

    items.emplace_back(new Apparel());
    items.emplace_back(new Ranged());
    items.emplace_back(new Melee());

    std::cout << "Inventory Types:\n";
    for (const auto& it: items)
        std::cout << it->type() << '\n';
}

见http://cpp.sh/6cjlt

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