Re: Storing a reference to the calling object

[Luis via Digitalmars-d-learn]

On Saturday, 23 May 2020 at 09:27:46 UTC, Tim wrote:
Hi all, I'm a little new to D and I'm wondering how I can store 
a reference to the calling object. I want to create a reference 
to an object's parent so that each time I go to update the 
sprite, it is able to grab its position from the parent.

So if I have:

class Sprite{
    /// Postional components of the sprite
    int* x, y;
    SDL_Surface* image_surface;
    auto parent;

    this(const char* path, auto parent){
        writeln(*x);
        this.parent = parent;
    }

    void update(){
        // Copy loaded image to window surface
        writeln("Sprites x: ",  *x);
        SDL_Rect dstRect;
        dstRect.x = parent.x;
        dstRect.y = parent.y;
        SDL_BlitSurface(image_surface, null, g_surface, 
&dstRect);
    }
}

And call it like so:

sprite = new Sprite(path, this);

How can I make this sort of thing work? Thanks a lot in advance 
for the help!

For example using a interface or a base class

```D
interface IBaseInterface
{
    int x();
    void x(int newX);

    int y()
    void y(int newY);

    ...
}

class Parent : IBaseInterface
{
    private int x, y;

    int x() { return this.x; }
    void x(int newX) { this.x = newX; }

    int y() { return this.y; }
    void y(int newY) { this. y = newY; }

    ...

    void f() {
        auto sprite = new Sprite("foo/bar/sprite.png", this);
        ...
    }
}


class Sprite{
    IBaseInterface parent;
    ...

    this(const char* path, IBaseInterface parent){
         writeln(*x);
         this.parent = parent;
    }

    void update(){
         // Copy loaded image to window surface
         writeln("Sprites x: ",  *x);
         SDL_Rect dstRect;
         dstRect.x = parent.x;
         dstRect.y = parent.y;
         SDL_BlitSurface(image_surface, null, g_surface, 
&dstRect);
    }
}
```