How does c++ keep things in scope? - c++

Question

To be more specific, I have a class that looks like this:
class Ball {
public:
unsigned collider_size;
scionofbytes::MovementComponent movement;
scionofbytes::GraphicComponent graphic;
Ball(u_int init_collider_size, std::string texture_path) {
collider_size = init_collider_size;
movement = scionofbytes::MovementComponent();
graphic = scionofbytes::GraphicComponent(
(u_int) collider_size/2,
(u_int) collider_size/2,
texture_path
);
}
};
I'm accepting the texture_path and passing it on to the graphic component, which looks like this:
class GraphicComponent {
unsigned height;
unsigned width;
public:
sf::Texture texture;
sf::Sprite sprite;
GraphicComponent() {}
GraphicComponent(unsigned init_height, unsigned init_width, std::string texture_path) {
width = init_width;
height = init_height;
texture.loadFromFile(texture_path);
sprite.setTexture(texture);
}
};
When I instantiate a ball object by passing in the texture_path, I'm creating a texture as a member of the graphic component and then assigning that texture to the graphic component's sprite member.
When using this sprite member to draw to the screen, I'm facing SFML's known white box problem.
Now from my understanding, of the ball objects stays alive, the graphic component member also stays alive as does the texture member of the graphic component.
So my question is, why does this not work? When using the sprite to draw on screen, I still get a white box. Why is the texture getting destroyed?

Answer 1

In your Ball class constructor you are making a copy of your GraphicComponent. IIRC sf::Sprite only holds a reference to the sf::Texture so your copy may end up with the sf::Sptite pointing to the deleted sf::Texture from the object it got copied from.
Try constructing your Ball without making a copy of your GraphicComponent:
class Ball {
public:
unsigned collider_size;
scionofbytes::MovementComponent movement;
scionofbytes::GraphicComponent graphic;
// Use initializer-list
Ball(u_int init_collider_size, std::string texture_path)
: collider_size(init_collider_size)
, movement()
, graphic((u_int) collider_size/2, (u_int) collider_size/2, texture_path)
{
// don't assign stuff here if you can avoid it
}
};
In addition to that you may also want to create a copy constructor for your GraphicComponent class to prevent corruption elsewhere:
class GraphicComponent
{
unsigned height;
unsigned width;
public:
sf::Texture texture;
sf::Sprite sprite;
GraphicComponent()
{
}
GraphicComponent(unsigned init_height, unsigned init_width,
std::string texture_path)
{
width = init_width;
height = init_height;
texture.loadFromFile(texture_path);
sprite.setTexture(texture);
}
// Give it a copy constructor
GraphicComponent(GraphicComponent const& other)
: height(other.height)
, width(other.width)
, texture(other.texture)
, sprite(texture) // make it point to the new Texture not the other one
{
}
};