如何在 c++ 中创建指针数组

Question

So I have a base class called items, 2 inherited classes from items called consumable and equipment, and 2 more inherited classes from each of those. Each have the function toString(), with it building up as you go down the inherited list. But here is my issu. I need to put 4 objects inherited from consumable and equipment into an array of items by pointers. How do I do that?

I have this code currently in my main:

Weapon greatSword("Great Sword", "A sword forged for mighty warriors", 12.50, true, 1, 150.00f, false, 13, "Slashing");
Armor mekiChestplate("Meki's Chest Plate", "A chest plate given to me by my mother", 1500.25f, false, 25, 2000.50f, true, "Chest", 18);
Food pie("Grandma's Pie", "Baked with love and affection", 10.35f, true, 5, 150, 0);
Potion spiderVenom("Spider's Venom", "Poision picked up from a spider", 100.55f, false, 10, 100, 1);

Item inventory[4]
{
    greatSword, 
    mekiChestplate,
    pie,
    spiderVenom
};

for(int i = 0; i < 4; i++)
{
    cout << inventory[i].toString() << endl;
    cout << "-----------------------------------------------------------" << endl;
}

return 0;

This works minus that they don't call their own toString, just the Item toString. How can I put the 4 items into an array of pointers?

Answer 1

As mentioned in comments above; the array should be an Item* type. Since question is posted as C++14, using <array> allows you to access the values by reference; instead of manually indexing. This is more scalable as the for loop doesn't have to be updated in the future. It also eliminates possible bugs or errors when the array size doesn't match the 'for' loop.

In order to access the child class function using the base class pointer, a virtual function needs to be defined. The example below demonstrates how to implement the virtual function in each class.

For bonus points, it also demonstrates how to call the parent's toString within each child class.

#include <array>
#include <string>
#include <iostream>

class Item
{
public:
    Item(const char* const name):
        mName(name)
    {}
    
    virtual std::string toString() const
    {
        return mName;
    }
private:
    std::string mName;    
    
};

class Equipment : public Item
{
public:
    Equipment(const char* const name):
        Item(name)
    {}
    
    virtual std::string toString() const override
    {
        const std::string extraInfo {"Equipment->"};
        const std::string item {Item::toString()};
        return extraInfo + item;
    }
};

class Consumable : public Item
{
public:
    Consumable(const char* const name):
        Item(name)
    {}
    
    virtual std::string toString() const override
    {
        const std::string extraInfo {"Consumable->"};
        const std::string item {Item::toString()};
        return extraInfo + item;
    }
};

class Weapon : public Equipment
{
public:  
    Weapon(const char* const name):
        Equipment(name)
    {}

    virtual std::string toString() const override
    {
        const std::string extraInfo {"Weapon->"};
        const std::string item {Equipment::toString()};
        return extraInfo + item;
    }
};

int main()
{
    Weapon greatSword("Great Sword");
    Weapon mekiChestplate("Meki's Chest Plate");
    Consumable pie("Grandma's Pie");
    Consumable spiderVenom("Spider's Venom");
    
    std::array<Item*, 4> inventory
    {
        &greatSword, 
        &mekiChestplate,
        &pie,
        &spiderVenom
    };
    
    for (auto it : inventory)
    {
        std::cout << it->toString() << std::endl;
        std::cout << "-----------------------------------------------------------" << std::endl;        
    }
    
    return 0;
}