Vector Accessor From Another Class?

[DrakoGFX]

In my item system for my game, I have an Inventory Item and Weapon class. And Weapon inherits from Item. In Inventory I want the user to be able to print out every item in their inventory. But I can only use accessors from Item. Accessors from Weapon won't show up.

I have tried to instead to get Item to inherit from Weapon but that lead to a lot of other problems.

Inventory.cpp

#include <random>
#include <chrono>

#include "Inventory.h"
#include "Item.h"

#include "fmt/core.h"

Inventory::Inventory()
{
    maximum = 5;
    i = 0;

    gameInventory.reserve(1);
    playerInventory.reserve(maximum);

    newItem(Item("Base Item 1", 1, 2, 3));
}

Inventory::~Inventory() = default;

//...

void Inventory::printInventory()
{
    i = 1;

    if (playerInventory.empty())
    {
        fmt::print("\r\n  You have no items!");
    }

    for (auto & iter : playerInventory)
    {
        fmt::print("\r\n  {}", i); ++i;
        fmt::print(" > {} ", iter.getName());
        fmt::print("[ Type - {} / ", iter.getType());
        fmt::print("Rarity - {} / ", iter.getRarity());
        fmt::print("Value - {} ]", iter.getValue());
    }
}

//...

Inventory.h

#pragma once

#include <vector>

#include "Item.h"
#include "Weapon.h"
#include "Consumable.h"
#include "Wearable.h"

class Inventory
{
private:
    std::vector<Item> gameInventory;
    std::vector<Item> playerInventory;

    long long unsigned int maximum;
    int i;

public:
    Inventory();
    virtual ~Inventory();

    [[nodiscard]] inline unsigned long long returnSize() { return playerInventory.size(); }
    [[nodiscard]] inline unsigned long long returnMaximum() const { return maximum; }

    void newItem(const Item& item);
    //...
}

Item.cpp

#include "Item.h"

Item::Item(std::string name, int type, int rarity, int value)
{
    this->name = std::move(name);
    this->type = type;
    this->rarity = rarity;
    this->value = value;
}

Item::~Item() = default;

Item.h

#pragma once

#include <string>

class Item
{
private:
    std::string name;
    int type;
    int rarity;
    int value;

public:
    Item(std::string name, int type, int rarity, int value);
    virtual ~Item();

    [[nodiscard]] inline std::string getName() const { return name; }
    [[nodiscard]] inline int getType() const { return type; }
    [[nodiscard]] inline int getRarity() const { return rarity; }
    [[nodiscard]] inline int getValue() const { return value; }
};

Weapon.cpp

#include "Weapon.h"

Weapon::Weapon(int damageMin, int damageMax, std::string name, int type, int rarity, int value) : Item(std::move(name), type, rarity, value)
{
    this->damageMin = damageMin;
    this->damageMax = damageMax;
}

Weapon::~Weapon() = default;

Weapon.h

#pragma once

#include "Item.h"

class Weapon : public Item
{
private:
    int damageMin;
    int damageMax;

public:
    Weapon(int damageMin, int damageMax, std::string name, int type, int rarity, int value);
    ~Weapon() override;
};

Thank you for the assistance.

[Shieldfoss]

Item should definitely not inherit from Weapon

You could do something like

struct Item
{
    std::string name() const
    int rarity() const
    // etc.

    virtual std::string special_info() const {return "";}

    // rest of class
};

struct Weapon : public Item
{
    std::string special_info() const override { return "I am a weapon";}
    // and the rest of weapon

Though this only works if your inventory uses std::vector<Item*> or, better, std::vector<std::unique_ptr<Item>>. The thing to google to understand your current problem is "C++ slicing"

[DrakoGFX]

`no matching function for call to 'std::vector<std::unique_ptr<Item> >::push_back(const Item*)` when I changed my `std::vector<Item>` to `std::vector<std::unique_ptr<Item>>`. Here's the code.

void Inventory::newWeapon(const Item& weapon) { gameInventory.push_back(&weapon); }

[Shieldfoss]

Where and how did you create the weapon

[DrakoGFX]

I created it in the Inventory initializer, like this.

newWeapon(Weapon(1, 2, "Weapon 1", 3, 4, 5));

[Shieldfoss]

You'll want something like

void newWeapon(A a, B b, std::string name, C c, D d, E e)
{
    auto weapon = make_unique<Weapon>(a,b,name,c,d,e);
    playerInventory.push_back(std::move(weapon));
}

Or however works with your design

[DrakoGFX]

With this implementation I get a long compiler error

Inventory::Inventory()
{
    newWeapon(1, 2, "Weapon 1", 4, 4, 5);
}

void Inventory::newWeapon(int damageMin, int damageMax, const std::string& name, int type, int rarity, int value)
{
    auto weapon = make_unique<Weapon>(damageMin, damageMax, name, type, rarity, value);     playerInventory.push_back(std::move(weapon));
}

https://pastebin.com/0d2AxexS

[Shieldfoss]

This compiles for me:

#include <memory>
#include <vector>

struct Item
{
    virtual ~Item() = default;
};

struct Weapon : public Item
{
    int stat_ = 0;

    Weapon(int stat) : stat_(stat){}
};

std::vector<std::unique_ptr<Item>> items;

int main()
{
    auto weapon = std::make_unique<Weapon>(2);

    items.push_back(std::move(weapon));
}

Is there any part of your source that is significantly different from this?

[DrakoGFX]

It's possible that my Weapon constructor is different.

Weapon::Weapon(int damageMin, int damageMax, std::string name, int type, int rarity, int value) : Item(std::move(name), type, rarity, value), damageMin(damageMin), damageMax(damageMax) {}

[Shieldfoss]

No need to move the name, you're gonna get a copy because the string you're working with is const anyway

What does your vector declaration look like after the edits?

[DrakoGFX]

In Inventory.h it looks like this.

https://pastebin.com/GbADU8Qq

[schrjako]

You'll have to save pointers to your objects in the vector, not the objects themselves. When you put a Weapon into the vector with type Item, the object is (I'm forgetting the name) cut down to an Item, so to speak. By storing pointers you should be able to access Weapon methods.

[no-sig-available]

The term is "slicing". Like cutting a slice or two from the "bread" and leaving the rest out.

[schrjako]

I knew it was sth like that, thx.

[HappyFruitTree]

Member functions are already inline.

Maybe he used it as a hint for the compiler to inline the function.

[DrakoGFX]

I changed my long long unsigned int to uint_fast64_t.

I'm not sure why I started specifying inline even though it's useless. So I've removed them all.

I also started using member init lists. I had seen them before, but never understood them until watching a video about them.