SFML texture holder deleted although still in scope - c++

Question

So I'm new to SFML. I read a lot of post, but I really don't get it.
I wrote an texture holder:
class tile_texture_holder {
private:
sf::Texture tx;
public:
tile_texture_holder(type a) {
switch (a) {
case type::desert:
tx.loadFromFile("C:/Users/Andreas/source/repos/conquer/Media/desert.png");
break;
case type::grass:
tx.loadFromFile("C:/Users/Andreas/source/repos/conquer/Media/grass.png");
break;
case type::mountain:
tx.loadFromFile("C:/Users/Andreas/source/repos/conquer/Media/mountain.png");
break;
case type::water:
tx.loadFromFile("C:/Users/Andreas/source/repos/conquer/Media/water.png");
break;
}
}
sf::Texture ret_texture() {
return tx;
}
~tile_texture_holder() {
std::cout << "///////////////////////HOLDER DELETED!!!/////////////////////" << std::endl;
}
};
And I tried to load a sprite with it in different ways....
For example:
tile_texture_holder t(type::desert);
sf::Sprite s;
s.setTexture(t.ret_texture());
(in the same function, where I draw the sprite)
I always get the white box being drawn. And I really dont get why the texture_holder is getting deleted.
BTW type is an enum.
I hope somebody can help me solve my issue!

Answer 1

s.setTexture(t.ret_texture());
in the line above you have undefined behaviour.
ret_texture returns temporary texture (it is returned by value, so a copy is made), setTexture takes reference to it, then at the end of expression temporary texture is destroyed and you have dangling reference in s.
Why this happens? Because setTexture of Sprite only holds reference to texture, it doesn't copy it.
According to SFML Sprite reference:
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.
Solution: ret_texture should return texture by reference.
sf::Texture& ret_texture() {
return tx;
}