How to loop through objects of a lua class

Question

local card = {x, y, w, h};

    function card:new(o, x, y, w, h)
        local o = o or {};
        setmetatable(o, self);
        self.__index = self;
        self.x = x;
        self.y = y;
        self.w = w;
        self.h = h;
        return o;
    end

How do i loop through objects created by this class?

Answer 1

There is no way to do this, unless you add some structure to explicitly track created objects in a table somewhere (probably with "weak" keys to allow them to be garbage collected).

It may be possible to traverse all local and global values to find tables that have __index value pointing to that card table, but it's unlikely to be practical.