My sfml ImageManager class is only displaying a white square in c++ - c++

Question

I know this topic is abundant in forums, but I need help for this specific issue. I'm following this tutorial to make a basic sfml ImageManager class for a tic tac toe game. I'm having trouble understanding how to implement this class in my game engine though. I'm going to post a lot of code as there are multiple classes involved:
Board.h: my tic-tac-toe game board.
#pragma once
#include "stdafx.h"
#include <vector>
#include "Box.h"
#include "SFML/Graphics.hpp"
#include "ImageManager.h"
class Board{
public:
Board();
~Board();
std::vector<Box> &GetBoxes();
sf::Sprite GetGameBoard();
private:
sf::Sprite gameBoard;
std::vector<Box> boxes;
};
And here's Board.cpp:
#include "stdafx.h"
#include "Board.h"
#include "SFML/Graphics.hpp"
Board::Board(){
ImageManager imgr;
imgr.AddResourceDirectory("images/");
gameBoard.setTexture(imgr.GetImage("images/t3board.png"));
}
Board::~Board(){
}
std::vector<Box> &Board::GetBoxes(){
return boxes;
}
sf::Sprite Board::GetGameBoard(){
return gameBoard;
}
Here's what is relevant from the ImageManager class from the tutorial:
const sf::Texture &ImageManager::GetImage(const std::string &filename){
for(std::map<std::string, sf::Texture>::const_iterator it = textures_.begin(); it != textures_.end(); ++it){
if(filename == it->first){
std::cout << "DEBUG_MESSAGE: " << filename << " using existing image.\n";
return it->second;
}
}
//if image doesn't exist (no need for else since it will return if filename is found
sf::Texture texture;
if(texture.loadFromFile(filename)){
//create both a string and matching image in the map
textures_[filename] = texture;
std::cout << "DEBUG_MESSAGE: " << filename << " loading image.\n";
return textures_[filename];
}
// If the image has still not been found, search all registered directories
//of course, it will be empty until I specify extra directories by adding them into the vector
for(std::vector< std::string >::iterator it = resourceDirectories_.begin(); it != resourceDirectories_.end(); ++it){
if(texture.loadFromFile((*it) + filename )){
textures_[filename] = texture;
std::cout << "DEBUG_MESSAGE: " << filename << " loading image 2.\n";
return textures_[filename];
}
}
//again, notice there's no elses because returns serve as breaks
std::cout << "GAME_ERROR: Image was not found. It is filled with an empty image.\n";
textures_[filename] = texture;
return textures_[filename];
}
Finally, in my engine, I get gameBoard and draw it to my window:
void Engine::Render(){
window.clear();
window.draw(board.GetGameBoard());
window.display();
}
My window just shows a complete white background, but it's still functional otherwise. Can anybody see what I've done wrong?

Answer 1

I assume that textures_ is a private member of the ImageManager class? In that case you have undefined behavior because ImageManager::GetImage returns a reference to data stored in a container that is destroyed (remember that imgr is a local variable in the constructor).

Answer 2

Ok I have it. It's a pretty embarrasing solution, but declaring my ImageManager imgr in the constructor of Board was destroying my ImageManager instantly, so I just cut that instance and pasted it in the header file. And for some reason returning a reference instead of the actual texture value was necessary, that also stumped me.