Const mismatches: 2 overloads have no legal conversion for 'this' pointer

Question

I'm getting this weird error:

error C2663: 'sf::Drawable::SetPosition' : 2 overloads have no legal conversion for 'this' pointer

I think it has something to do with const mismatches but I don't know where, or why. In the following code I have a vector of shapes and sprites, and when trying to access one of the vectors shapes and calling one of its functions I'm getting the error.

std::vector<sf::Shape> Shapes;
std::vector<sf::Sprite> Sprites;

bool AddShape(sf::Shape& S){
    Shapes.push_back(S); return true;
};
bool AddSprite(sf::Sprite& S){
    Sprites.push_back(S); return true;
};

private:

virtual void Render(sf::RenderTarget& target) const {                
    for(unsigned short I; I<Shapes.size(); I++){
        Shapes[I].SetPosition(
            Shapes[I].GetPosition().x + GetPosition().x,
            Shapes[I].GetPosition().y + GetPosition().y);
        target.Draw(Shapes[I]);
    }
    for(unsigned short I; I<Sprites.size(); I++){
        target.Draw(Sprites[I]);
    }
}

How can I fix this?

Answer 1

Render is declared with a const after the parameters. This means it does not change its object. Which means, that all of the object's member variables are considered constants within Render, as changing their state means changing the containing object. Assuming Shapes is a member variable, and that SetPosition does change the shape (i.e. not declared as const), you cannot call it within a const member function.

So, remove the const from Render and you'll be fine (you fix your logic, in case it must be const).