States are used to separate the global states a game can be in (say, the front-end menu, ingame, the help menu etc).

States are implemented by using three classes: StateBase, State and 
StateManager.
- StateBase is an abstract base class that provides functions for handling
events and logic and for rendering screens. The states will then inherit
from this class.
- State is a handle class that takes responsibility for handling the
complexity created by polymorphic use of states.
- StateManager manages a State stack. The idea of the State stack is that the
top element of the stack is the state that is in use (the so-called current
stack).

#ifndef STATEBASE_H
#define STATEBASE_H

//Descr: The abstract base class of all the states.
/////////////////////////////////////////////////////////////////////


#include "SDL/SDL.h"

class StateBase {
	friend class State;
public:
	virtual ~StateBase();

	virtual bool HandleEvents() = 0;
	virtual bool HandleLogic() = 0;
	virtual bool RenderScreen(SDL_Surface*) = 0;

protected:
	// Clone() makes a copy of the object it is called from and returns
	// a pointer that points to that copy.
	virtual StateBase* Clone() const = 0;
};

#endif

#ifndef STATE_H
#define STATE_H

//Descr: State is a handle class for the classes that derive from
// the abstract base class Statebase. It's purpose is to hide the
// complexity caused by polymorphic use of the classes from the user.
/////////////////////////////////////////////////////////////////////

#include "StateBase.h"

// State ID's are unique labels that are given to states. Additional
// states that are created should have their own ID.
enum StateId { 
	STATE_NULL,  // Not an actual state. Used to communicate "no state".
	STATE_FEMENU, // The front-end menu state.
	STATE_INGAME // Ingame state. Should be sufficient for simple games.
};

class State {
public:
	// Needed constructors and assignment operator.
	State(StateId sid);
	State& operator=(const State& sc);
	~State() { delete s; }
	
	// All the work is simply forwarded to the state pointed to by s.
	bool HandleEvents()                  { return s->HandleEvents(); }
	bool HandleLogic()                   { return s->HandleLogic(); }
	bool RenderScreen(SDL_Surface* surf) { return s->RenderScreen(surf); }

private:
	// s points to an actual state.
	StateBase* s; 
};

#endif

#include "State.h"
#include "InGame.h"
#include <stdexcept>

using std::invalid_argument;

State::State(StateId sid)
{
	switch (sid) {
		/*case STATE_FEMENU:
			s = new FEMenu;
			break;*/
		case STATE_INGAME:
			s = new InGame;
			break;
		default:
			throw invalid_argument("The state ID is invalid.");
	}
}

State& State::operator=(const State& sc)
{
	// If the object isn't being assigned to itself
	if (&sc != this) {
		// delete the current state object pointed to 
		delete s;
		// and point to a clone of the other state object.
		s = sc.s->Clone();
	}
	return *this;
}

#ifndef STATEMANAGER_H
#define STATEMANAGER_H

//Descr: The statemanager manages a stack of states. It can change
//       states in three ways: by pushing a state on top of the
//       current state, by popping the current state on the stack and
//       by replacing the current state with a new one.
//Notes: The current state is always the top element of the stack.
/////////////////////////////////////////////////////////////////////

#include "State.h"
#include <stack>

class StateManager {
	// Type to describe methods of state changing.
	enum ChangeMethod {
		CM_NULL,
		CM_REPLACE,
		CM_PUSH,
		CM_POP
	};

public:
	// Initialize the implementation variables.
	StateManager(): nextStateId(STATE_NULL), isKilled(false), changeMethod(CM_NULL) { }

	// Set next state, which will replace the current state.
	bool NextStateReplace(StateId newState);
	// Set next state, which will be stacked on top of the current one.
	void NextStatePush(StateId newState);
	// Set next state to be the state under the current state in the stack,
	// deleting the current state in the process.
	bool NextStatePop();
	// Actually change to the next state, if there is one.
	bool ChangeState();

	// Returns a reference to the current state.
	State& CurrentState()  { return stateStack.top(); }

	// Kill the statemanager.
	void Kill() { isKilled = true; }
	// Check if the statemanager has been killed.
	bool IsKilled() { return isKilled; }

private:
	std::stack<State> stateStack;
	StateId nextStateId;
	bool isKilled;
	ChangeMethod changeMethod;	
};

#endif

#include "StateManager.h"

using std::stack;

bool StateManager::NextStateReplace(StateId newState)
{
	if(stateStack.empty() == false) {
		nextStateId = newState;
		changeMethod = CM_REPLACE;
		return true;
	} else
		return false;
}

void StateManager::NextStatePush(StateId newState)
{	
	nextStateId = newState;
	changeMethod = CM_PUSH;
}

bool StateManager::NextStatePop()
{
	if(stateStack.size() > stack<State>::size_type(1)) {
		changeMethod = CM_POP;
		return true;
	} else
		return false;
}

bool StateManager::ChangeState()
{
	switch(changeMethod) {
		case CM_NULL:
			return false;
		case CM_REPLACE:
			stateStack.top() = State(nextStateId);
			break;
		case CM_PUSH:
			stateStack.push(State(nextStateId));
			break;
		case CM_POP:
			stateStack.pop();
			break;
	}
	nextStateId = STATE_NULL; // RESET
	changeMethod = CM_NULL;   // RESET
	return true;
}

#ifndef INGAME_H
#define INGAME_H

#include "StateBase.h"
#include "Button.h"

class InGame: public StateBase {
public:
	InGame()  { quit = new Button("quit.png", 20, 20); }
	~InGame() { delete quit; }

	bool HandleEvents();
	bool HandleLogic();
	bool RenderScreen(SDL_Surface*);

protected:
	InGame* Clone() const { return new InGame(*this); }

private:
	Button* quit;
};

#endif

#include "InGame.h"

bool InGame::HandleEvents()
{
	return true; // Not yet finished...
}

bool InGame::HandleLogic()
{
	return true; // Not yet finished...
}

bool InGame::RenderScreen(SDL_Surface *)
{
	return true; // Not yet finished...
}

Quote:Compiling... main.cpp SDLVideo.cpp Ingame.cpp c:\program files\microsoft visual studio 8\vc\include\xlocnum(590) : warning C4312: 'type cast' : conversion from 'uintptr_t' to 'void *' of greater size c:\program files\microsoft visual studio 8\vc\include\xlocnum(566) : while compiling class template member function 'std::istreambuf_iterator<_Elem,_Traits> std::num_get<_Elem,_InIt>::do_get(_InIt,_InIt,std::ios_base &,std::ios_base::iostate &,void *&) const' with [ _Elem=char, _Traits=std::char_traits, _InIt=std::istreambuf_iterator> ] c:\program files\microsoft visual studio 8\vc\include\xlocnum(1365) : see reference to class template instantiation 'std::num_get<_Elem,_InIt>' being compiled with [ _Elem=char, _InIt=std::istreambuf_iterator> ] c:\program files\microsoft visual studio 8\vc\include\xlocnum(590) : warning C4312: 'type cast' : conversion from 'uintptr_t' to 'void *' of greater size c:\program files\microsoft visual studio 8\vc\include\xlocnum(566) : while compiling class template member function 'std::istreambuf_iterator<_Elem,_Traits> std::num_get<_Elem,_InIt>::do_get(_InIt,_InIt,std::ios_base &,std::ios_base::iostate &,void *&) const' with [ _Elem=wchar_t, _Traits=std::char_traits, _InIt=std::istreambuf_iterator> ] c:\program files\microsoft visual studio 8\vc\include\xlocnum(1371) : see reference to class template instantiation 'std::num_get<_Elem,_InIt>' being compiled with [ _Elem=wchar_t, _InIt=std::istreambuf_iterator> ] State.cpp c:\program files\microsoft visual studio 8\vc\include\xlocnum(590) : warning C4312: 'type cast' : conversion from 'uintptr_t' to 'void *' of greater size c:\program files\microsoft visual studio 8\vc\include\xlocnum(566) : while compiling class template member function 'std::istreambuf_iterator<_Elem,_Traits> std::num_get<_Elem,_InIt>::do_get(_InIt,_InIt,std::ios_base &,std::ios_base::iostate &,void *&) const' with [ _Elem=char, _Traits=std::char_traits, _InIt=std::istreambuf_iterator> ] c:\program files\microsoft visual studio 8\vc\include\xlocnum(1365) : see reference to class template instantiation 'std::num_get<_Elem,_InIt>' being compiled with [ _Elem=char, _InIt=std::istreambuf_iterator> ] c:\program files\microsoft visual studio 8\vc\include\xlocnum(590) : warning C4312: 'type cast' : conversion from 'uintptr_t' to 'void *' of greater size c:\program files\microsoft visual studio 8\vc\include\xlocnum(566) : while compiling class template member function 'std::istreambuf_iterator<_Elem,_Traits> std::num_get<_Elem,_InIt>::do_get(_InIt,_InIt,std::ios_base &,std::ios_base::iostate &,void *&) const' with [ _Elem=wchar_t, _Traits=std::char_traits, _InIt=std::istreambuf_iterator> ] c:\program files\microsoft visual studio 8\vc\include\xlocnum(1371) : see reference to class template instantiation 'std::num_get<_Elem,_InIt>' being compiled with [ _Elem=wchar_t, _InIt=std::istreambuf_iterator> ] StateManager.cpp Button.cpp c:\program files\microsoft visual studio 8\vc\include\xlocnum(590) : warning C4312: 'type cast' : conversion from 'uintptr_t' to 'void *' of greater size c:\program files\microsoft visual studio 8\vc\include\xlocnum(566) : while compiling class template member function 'std::istreambuf_iterator<_Elem,_Traits> std::num_get<_Elem,_InIt>::do_get(_InIt,_InIt,std::ios_base &,std::ios_base::iostate &,void *&) const' with [ _Elem=char, _Traits=std::char_traits, _InIt=std::istreambuf_iterator> ] c:\program files\microsoft visual studio 8\vc\include\xlocnum(1365) : see reference to class template instantiation 'std::num_get<_Elem,_InIt>' being compiled with [ _Elem=char, _InIt=std::istreambuf_iterator> ] c:\program files\microsoft visual studio 8\vc\include\xlocnum(590) : warning C4312: 'type cast' : conversion from 'uintptr_t' to 'void *' of greater size c:\program files\microsoft visual studio 8\vc\include\xlocnum(566) : while compiling class template member function 'std::istreambuf_iterator<_Elem,_Traits> std::num_get<_Elem,_InIt>::do_get(_InIt,_InIt,std::ios_base &,std::ios_base::iostate &,void *&) const' with [ _Elem=wchar_t, _Traits=std::char_traits, _InIt=std::istreambuf_iterator> ] c:\program files\microsoft visual studio 8\vc\include\xlocnum(1371) : see reference to class template instantiation 'std::num_get<_Elem,_InIt>' being compiled with [ _Elem=wchar_t, _InIt=std::istreambuf_iterator> ] Generating Code... Compiling manifest to resources... Linking... !!!FIXEDState.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall StateBase::~StateBase(void)" (??1StateBase@@UAE@XZ) referenced in function __unwindfunclet$??0InGame@@QAE@XZ$0 FIXED!!! StateManager.obj : error LNK2019: unresolved external symbol __imp___CrtDbgReportW referenced in function "public: class State const & __thiscall std::_Deque_const_iterator,1>::operator*(void)const " (??D?$_Deque_const_iterator@VState@@V?$allocator@VState@@@std@@$00@std@@QBEABVState@@XZ) C:\Projects\Application\Debug\Application.exe : fatal error LNK1120: 2 unresolved externals

virtual ~StateBase();

virtual ~StateBase() {}

Quote:Original post by jyk
One quick observation: it looks like ~StateBase() is declared, but not defined. Try changing:

virtual ~StateBase();

To:

virtual ~StateBase() {}

There are obviously some other things going on as well, but this might clear up one of your errors.

Quote:Original post by jyk
One other note - other design issues aside, using 'smart' rather than 'raw' pointers throughout will get rid of some of the manual memory management you have in place currently (which in turn will make your code cleaner, clearer, and less error-prone).

Quote:Original post by fpsgamer
You clearly have a template error. The bad news is that with templates often commenting out a few lines at a time is the most effective way to debug.

You can also look into a tool that can translate those damn template errors into "english"