sprite out of scope because it's local - c++

Question

I'm having trouble implementing this function.
//Engine.cpp
void Game::createPlayer(sf::Sprite &player)
{ ///Can't get this to work
sf::Texture player_texture;
if (!player_texture.loadFromFile("player.png"))
{
//Error Loading
}
player.setTexture(player_texture);
}
I want it to replace the "creates player in void Game::run but I realize that Player_texture is local to Createplayer and that it won't exist when the function returns.
void Game::run()
{
sf::RenderWindow window(sf::VideoMode(SCREEN_X, SCREEN_Y), "Shogun Master");
srand((unsigned int)time(NULL));
//Creates Player [Makes into function]
sf::Texture player_texture;
player_texture.loadFromFile("sprites/player.png");
sf::Sprite player(player_texture);
//Creates Enemy [Make into function]
sf::Texture enemy_texture;
enemy_texture.loadFromFile("sprites/enemy.png");
sf::Sprite enemy[MAX_ENEMIES];
for (int x = 0; x < MAX_ENEMIES; x++)
{
enemy[x].setTexture(enemy_texture);
enemy[x].setPosition(rand_int(100, SCREEN_X - 100), rand_int(100, SCREEN_Y - 100)); //Spawning Point
}
//Sets Positions
player.setPosition(500, 300);
while (window.isOpen())
{
sf::Event event;
while (window.pollEvent(event))
{
check_closeWindows(event, window); //Closes Game if Executed
player_movement(event); //Moves Character
attack(event); //Character's attacks
}
border(player); //Border so player does not go off screen
for (int x = 0; x < total_enemies; x++)
border(enemy[x]);
movementUpdate(player, enemy); //Player & Enemy Movement Updates
collision(player, enemy[0]);
window.clear();
window.draw(player); //Draws Player
for (int x = 0; x < total_enemies; x++)
window.draw(enemy[x]); //Draws Enemy
window.display();
}
}
so how would I implement this, so that my sprite doesn't return a white box because it went out of scope.
//Engine.h
void Game::createPlayer(sf::Sprite &player);

Answer 1

The documentation (http://www.sfml-dev.org/documentation/2.0/classsf_1_1Sprite.php#a3729c88d88ac38c19317c18e87242560) for the setTexture() method you're calling says:
The texture argument refers to a texture that must exist as long as the sprite uses it. Indeed, the sprite doesn't store its own copy of the texture, but rather keeps a pointer to the one that you passed to this function. If the source texture is destroyed and the sprite tries to use it, the behaviour is undefined.
One way to deal with this would be to make your own struct or class which contains both the Sprite and its texture:
struct SpriteWithTexture
{
sf::Texture texture;
sf::Sprite sprite;
SpriteWithTexture()
{
sprite.setTexture(texture);
}
SpriteWithTexture(const SpriteWithTexture& that)
: texture(that.texture)
{
sprite.setTexture(texture);
}
SpriteWithTexture& operator=(const SpriteWithTexture& that)
{
texture = that.texture;
sprite.setTexture(texture);
return *this;
}
};
Then you can return this from your function:
SpriteWithTexture Game::createPlayer()
{
SpriteWithTexture player;
if (!player.texture.loadFromFile("player.png"))
{
//Error Loading
}
return player;
}
Now the texture will always live as long as the sprite.
Note however that when you construct your "enemies" you use a single texture for all of them. To enable sharing one texture between many sprites, we can enhance the above:
struct SpriteWithTexture
{
std::shared_ptr<sf::Texture> texture;
sf::Sprite sprite;
SpriteWithTexture(const std::shared_ptr<sf::Texture>& texture_)
: texture(texture_)
{
sprite.setTexture(*texture);
}
};
Now you can use it this way:
std::shared_ptr<sf::Texture> player_texture(new sf::Texture);
player_texture->loadFromFile("sprites/player.png");
SpriteWithTexture player(player_texture);
std::shared_ptr<sf::Texture> enemy_texture(new sf::Texture);
enemy_texture->loadFromFile("sprites/enemy.png");
std::vector<SpriteWithTexture> enemies;
for (int x = 0; x < MAX_ENEMIES; x++)
{
enemies.emplace_back(enemy_texture); // construct enemy Sprite
enemies.back().sprite.setPosition(rand_int(100, SCREEN_X - 100), rand_int(100, SCREEN_Y - 100)); //Spawning Point
}
Now all the enemies in the vector share a single texture. Maybe this matters for efficiency.