Class Definition

[Ramzi89]

Can anyone see whats wrong this class definition. The compiler is throwing out the following error:

/tmp/cccWQe0N.o: In function `Item::Item(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int)':
qu7.cpp:(.text+0xc): undefined reference to `vtable for Item'
/tmp/cccWQe0N.o:(.rodata._ZTI8Painting[typeinfo for Painting]+0x8): undefined reference to `typeinfo for Item'
collect2: ld returned 1 exit status

 class Item
{
private: 
	string sellername;
	int price;
public: 
	Item(string sellername1, int price1);
virtual void display();
friend class Painting;
};

Item::Item(string sellername1, int price1)
{
sellername = sellername1;
price = price1;
}

[Ramzi89]

Basically its something to do with the friend class. I whipped out the friend class and moved private members to public and the same error was thrown out.

Here is the derived class definition:

class Painting : public Item{
	private:
	int medium;

	public:
	Painting(string sellername1, int price, int medium);
	virtual void display();
};

and the derived class constructor:

Painting::Painting(string sellername1, int price1, int medium1):Item(sellername1, price1)
{
	medium = medium1;
}

[Ramzi89]

The solution is to ensure that all virtual methods that are not pure are defined. Note that a destructor must be defined even if it is declared pure-virtual [class.dtor]/7.

Yeah so i defined virtual void display() and everything was cool.

Basically if you see undefined reference to vtable then define ur virtual classes unless they are pure virtual!!!

[zb0S216C]

Are you providing a definition for "Item::display( )"? Also, if your class contains a virtual member-function, the chances are you need a virtual destructor as well.

Edit: I see you did eventually provide a definition for "Item::display( )". Also, pure-virtual functions have to have a definition.

_Wazzak