Question

I’m learning C++ by myself, “creating” a RPG. However, I’m stuck at point of creating a class named Item, which would be the base class for all game items (or if it was in Java, an interface). Here’s my code:

class Item {

    public:

    virtual const char* GetName() = 0;
};

I read something about “pure virtual” functions, which I’m using.

My Character class, where I use my Item:

class Character {

  // some code...

  void ConsumeItem(Item item);

}

But gcc gives me this error:

g++ -Wall -o adventure character.cpp adventure.cpp
In file included from adventure.cpp:3:0:
character.h:36:24: error: cannot declare parameter ‘item’ to be of abstract type ‘Item’
item.h:4:7: note:   because the following virtual functions are pure within ‘Item’:
item.h:11:22: note:     virtual const char* Item::GetName()

I’m very new to OOP in C++, as it is very different from Java. I already read some articles about abstract classes in C++, but I just can’t get it working.

Can you please tell me the right way to achieve this?

Answer 1

In Java, doing something like that will create a reference to an Item, which you can then assign an instance of a concrete subclass.

However in C++, Item item will create an instance of Item, which isn’t allowed since Item contains a pure virtual function.

To avoid this problem, you need to make item a pointer or a reference, like:

void ConsumeItem(Item *item);