Re: Aliasing member's members

[TheFlyingFiddle via Digitalmars-d-learn]

On Monday, 26 February 2018 at 20:50:35 UTC, Kayomn wrote:
I've been experimenting with D's Better C mode, and I have a 
question regarding something that I started thinking about 
after watching one of Jonathon Blow's talks on data-oriented 
programming - more specifically the aspect of fake "inheritance"

I have the following code. My question is if it's possible to 
use alias in a similar way to Jonathon's own language Jai and 
its using keyword, referencing the internal Vector2 as 
Player.pos instead of Player.entity.position:

import core.stdc.stdio : printf;

uint idCounter = 0;

struct Vector2 {
        double x,y;
}

struct Entity {
        uint id;
        Vector2 position;
}

struct Player {
        Entity entity;

        alias pos = Entity.position;
}

Player createPlayer(Vector2 position) {
        Player player;
        player.entity.id = idCounter++;
        player.entity.position = position;

        return player;
}

int main(string[] args) {
        Player player = createPlayer(Vector2(50.0,50.0));

        printf(
                "[Player]\nid: %d\nPosition: %lf x %lf\n",
                player.entity.id,
                player.pos.x,
                player.pos.y
        );

        return 0;
}

Don't think you can alias member variables directly.

You could do this though:

struct Player {
    Entity entity;

    ref auto pos() inout { return entity.position; }
}

Which will give you most of what you want. Although if you want 
to take the address of pos you have to use

auto addr = &player.pos();