Duplicate symbol error in C++ and Xcode

Question

I'm trying to declare a class that acts as enum. But if I include it more than once, I get several "duplicated symbol" errors.

This my ItemType.h file

#ifndef DarkSnake_ItemType_h
#define DarkSnake_ItemType_h

#define COLOR_ITEM_1 0xffff00ff
#define COLOR_ITEM_2 0xffff03ff
#define COLOR_ITEM_3 0xffff06ff

class ItemType {
public:
    static const ItemType NONE;
    static const ItemType ITEM_1;
    static const ItemType ITEM_2;
    static const ItemType ITEM_3;

    static ItemType values[];

    static ItemType getItemTypeByColor(const int color) {
        for (int i = 0; 3; i++) {
            if (color == values[i].getItemColor()) {
                return values[i];
            }
        }
        return NONE;
    }


    bool operator ==(const ItemType &item) const;
    bool operator !=(const ItemType &item) const;


    int getItemColor() { return this->color; };

private:
    const int color;
    ItemType(const int _color) : color(_color) {}
};

bool ItemType::operator == (const ItemType &item) const {
    return this->color == item.color;
}

bool ItemType::operator != (const ItemType &item) const {
    return this->color != item.color;
}

#endif

And this my ItemType.cpp:

#include "ItemType.h"


const ItemType ItemType::NONE   = ItemType(0);
const ItemType ItemType::ITEM_1 = ItemType(COLOR_ITEM_1);
const ItemType ItemType::ITEM_2 = ItemType(COLOR_ITEM_2);
const ItemType ItemType::ITEM_3 = ItemType(COLOR_ITEM_3);

ItemType ItemType::values[] = {ItemType::ITEM_1, ItemType::ITEM_2, ItemType::ITEM_3};

In a first attempt I tried to put the C++ code into the header file, and I got the same errors. But now I don't know what am I doing wrong.

Can you help me, please?

Many thanks!

Answer 1

You can't define non-inline functions outside a class in a header file.

To solve this, you have three possibilities:

1. Move the definitions of operator== and operator!= inside the class definition.
2. Move the definitions to ItemType.cpp.
3. Declare the functions inline.