Possible Duplicate:
“Undefined reference to” template class constructor
I've just started using templates, and I was wandering whether or not it is actually legal to call a template function in a child class. My problem is with the Template function ChangeSprite in the code below. It is being called in a child class, but this creates a linking error. If I remove the template part, and just give it one of the multiple things I plan on using it with instead it works fine, so I'm fearing that I won't be able to do this.
//base class
#pragma once
#include "Tile.h"
#include <list>
#include "Sprite.h"
#include "WindowCreater.h"
#include "Directx.h"
#define LeftClickParameters WindowCreator *gw, Mouse* mouse
struct Grid
{
SPRITE *sprite;
int width, hieght;
int w, h;
int x, y;
Grid(int width, int hieght,SPRITE *sprites);
list<Tile> tilew;
list<list<Tile>> tileh;
//methods
void savefile();
void openfile();
virtual void MoveLeft() = 0;
virtual void MoveRight() = 0;
virtual void MoveUp() = 0;
virtual void MoveDown() = 0;
virtual void addrow() = 0;
virtual void deleterow() = 0;
virtual void addcolumb() = 0;
virtual void deletecolumb() = 0;
//template functions
template <class T> void ChangeSprite(SPRITE *newSprite,list<T> tilew,list<list<T>> tileh);
// Virtual methods
virtual list<Tile> ReadTiles() = 0;
};
and this is where it is being called
//how the function is being called
void Map::Brush(SPRITE *newSprite, POINT MousePosition)
{
Grid::ChangeSprite<MapTile>(newSprite,mapTilew,mapTileh);
}
It can as long as Map
inherits from Grid
otherwise, you would have to make ChangeSprite
static, or give it a Map
object to act on. Here's a valid example of a child calling the parents templated function.
struct Grid {
template <class T> void ChangeSprite(/*params here*/) {
// code here
}
};
struct Map : public Grid {
void Brush() {
// bool being a placeholder for MapTile
Grid::ChangeSprite<bool>(/*params here*/) {
// code here
}
}
};
Your problem probably lies in the different files you're using, for instance templated functions should be defined in the header file, in or below your class definition.