Heyas, I just tried to add some very basic collision detection to my 2D game. I don't really think I am going in the right direction with implementing this, I keep getting a linker error now. I have narrowed this linker down to a problem with to where I declare two functions. Here is the entire error: 2dEp error LNK2019: unresolved external symbol "private: int __thiscall CGame::CheckCollision(class CMap &,class CSprite &,char)" (?CheckCollision@CGame@@AAEHAAVCMap@@AAVCSprite@@D@Z) referenced in function "public: void __thiscall CGame::Loop(class CMap &,class CSprite &)" (?Loop@CGame@@QAEXAAVCMap@@AAVCSprite@@@Z) Here is the code:

// game.h


#include "sprite.h"
#include "map.h"

class CGame
{
	public:
		CGame();					// Constructor

		~CGame();					// Destructor

		void Launch();
		void Loop(CMap &Map, CSprite &Sprite);

	private:
            //  This is what causes the error, if i comment it out everything compiles fine.

		int CheckCollision(CMap &Map, CSprite &Sprite, char direction);
};

// game.cpp

// Game Loop

void CGame::Loop(CMap &Map, CSprite &Sprite)
{
	// This will be the game loop

	Map.LoadTiles();
	Map.LoadMap();
	Sprite.LoadSprite();
	Map.DrawBG();
	Map.DrawSprite(Sprite.ShowSrcRect(), Sprite.ShowDstRect(), Sprite.SpriteSurface);

	SDL_Event l_Event;
	bool l_GameBool = true;
	char l_dir = NULL;

	while (l_GameBool == true)
	{
		if (SDL_PollEvent(&l_Event) == 1)
		{
			switch(l_Event.type)
			{
				case SDL_QUIT:
					l_GameBool = false;
					break;
				case SDL_KEYDOWN:
					switch(l_Event.key.keysym.sym)
					{
					case SDLK_UP:
						l_dir = 'u';
						CheckCollision(Map, Sprite, l_dir);
						break;
					case SDLK_DOWN:
						l_dir = 'd';
						CheckCollision(Map, Sprite, l_dir);
						break;
					case SDLK_RIGHT:
						l_dir = 'r';
						CheckCollision(Map, Sprite, l_dir);
						break;
					case SDLK_LEFT:
						l_dir = 'l';
						CheckCollision(Map, Sprite, l_dir);
						break;
					case SDLK_ESCAPE:
						l_GameBool = false;
						break;
					}
					break;
			}
			Map.DrawBG();
			Map.DrawSprite(Sprite.ShowSrcRect(), Sprite.ShowDstRect(), Sprite.SpriteSurface);
			Map.Update();
		}
	}
}
// Check Collision Detection Function

int CheckCollision(CMap &Map, CSprite &Sprite, char direction)
{
	int liReturn = 0;
	
	int liSpriteXTile = Sprite.ShowXPos() / 30;
	int liSpriteYTile = Sprite.ShowYPos() / 30;

	switch(direction)
	{
	case 'u':
		if (Map.TileStatus(liSpriteXTile+1, liSpriteYTile) == 0)
		{
			Sprite.StepUp();
		} else {
			liReturn = 0;
		}
		break;
	case 'd':
		if (Map.TileStatus(liSpriteXTile-1, liSpriteYTile) == 0)
		{
			Sprite.StepDown();
		} else {
			liReturn = 0;
		}
		break;
	case 'r':
		if (Map.TileStatus(liSpriteXTile, liSpriteYTile+1) == 0)
		{
			Sprite.StepRight();
		} else {
			liReturn = 0;
		}
		break;
	case 'l':
		if (Map.TileStatus(liSpriteXTile, liSpriteYTile-1) == 0)
		{
			Sprite.StepLeft();
		} else {
			liReturn = 0;
		}
		break;
	default:
		fprintf(stderr, "\nCollision Detection error: Invalid direction parameter\n");
		break;
	}
	return liReturn;
}

I know that the Step functions work, I had those moving the sprite around before I tried added the Collision detection. Could someone help me with this linker error? And perhaps some tips on how I am structuring the code? I personally believe this isn't really the most efficient way to be structuring my code. It works(or did before I made this recent change), but I can see it getting fairly messy soon. Particularly with the classes not being completely independent of each other. I am still very new with SDL and fairly new with classes. Any tips would be very appreciated. Thanks, Chris edit: The error would probably have helped... [edited by - Chryzmo on May 20, 2004 8:41:05 PM]

Change
int CheckCollision(CMap &Map, CSprite &Sprite, char direction)
to
int CGame::CheckCollision(CMap &Map, CSprite &Sprite, char direction)