Linker errors with static abstract class...
Hello, I'm trying to do this:
Code:
#include "stdafx.h"
#include "Menu_State.h"
#include "Play_State.h"
#include "IO.H"
void Menu_State::handle_events(State_Manager * state_manager)
{
result = IO::instance().get_input();
switch(result)
{
case 1: // play blackjack
state_manager->change_state(Play_State::Instance());
/*
if(players.size() == 0)
{
initialize_players(2);
}
pot = new Pot;
deck = new Deck;
deck->shuffle_deck();
players[0].draw(*(deck), 2);
players[1].draw(*(deck), 1);
return 3;
case 2: // quit game
return 4;
default:// invalid entry
std::cout << "Please enter 1 or 2.\n";
return 0;
*/
}
}
I've bolded the error producing line. It's a function that returns a static instance of the Play_State class, it is a singleton.
Code:
#ifndef PLAY_STATE_H
#define PLAY_STATE_H
#include "Gamestate.h"
class Play_State : public Gamestate
{
public:
void init();
void cleanup();
void handle_events(State_Manager * state_manager);
void update();
void print();
static Play_State * Instance()
{
return &play_instance;
}
protected:
Play_State() {};
private:
static Play_State play_instance;
};
#endif
I've done something similar to this before and never got a linker error, although I've never done this with a derived class before...
Here is the Gamestate abstract class:
Code:
#ifndef GAMESTATE_H
#define GAMESTATE_H
#include "State_Manager.h"
class State_Manager;
class Gamestate
{
public:
virtual void init() = 0;
virtual void cleanup() = 0;
virtual void update(State_Manager * state_manager) = 0;
virtual void print(State_Manager * state_manager) = 0;
virtual void handle_events(State_Manager * state_manager) = 0;
void change_state(State_Manager * state_manager, Gamestate * state);
protected: Gamestate() { }
};
#endif
I'm getting error messages when trying to grab an instance of the Play_State.
Code:
------ Build started: Project: Blackjack, Configuration: Debug Win32 ------
Compiling...
Menu_State.cpp
Generating Code...
Skipping... (no relevant changes detected)
Play_State.cpp
Linking...
Menu_State.obj : error LNK2001: unresolved external symbol "private: static class Play_State Play_State::play_instance" (?play_instance@Play_State@@0V1@A)
C:\Documents and Settings\jcoleman\Desktop\Blackjack\Debug\Blackjack.exe : fatal error LNK1120: 1 unresolved externals
Build log was saved at "file://c:\Documents and Settings\jcoleman\Desktop\Blackjack\Blackjack\Debug\BuildLog.htm"
Blackjack - 2 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
Any ideas as to why this is happening?
