Lua 2d array defined in object uses pass by reference

Question

I have the following object:

local Game = {}
function Game:new(aNumberOfPlayers, aPlayer1, aPlayer2)
    self.NumberOfPlayers = aNumberOfPlayers
    self.Player1 = aPlayer1
    self.Player2 = aPlayer2
    self.Id = HttpService:GenerateGUID(true)
    self.Status = "Waiting"
    self.Moves = {}
    self.Position = GetInitialGamePosition()
    return self
end

local Square = {}
function Square:new(x, y, index, color)
    self.X = x
    self.Y = y
    self.Index = index
    self.Color = color
    return self
end

That uses following function to intialize the 2d array for Position

function GetInitialGamePosition()
    local mt = {}   -- create the matrix
    for i=1,15 do
        mt[i] = {}
        for j=1,15 do
            mt[i][j] = Square:new(i,j,GetIndexFromRowColumn(i,j),nil)
        end
    end
    return mt
end

Problem here is that since tables pass by reference each element of the 2d array ends up being the same. In other words when i iterate over a Position every element has same row, column, and index. Not sure what the best way to get around this is?

@ Egor Skriptunoff So the game object ends up with an array with 15 rows and 15 columns which each contain a square object. Each square object has X=15, Y=15, and index of 225. Basically treating row, column, and index as global variables — Maxqueue
– Maxqueue, Commented Oct 3, 2020 at 23:23

Egor Skriptunoff · Accepted Answer · 2020-10-03 23:27:31Z

1

function Square:new(x, y, index, color)
    local o = {}
    o.X = x
    o.Y = y
    o.Index = index
    o.Color = color
    setmetatable(o, self)
    self.__index = self
    return o
end

answered Oct 3, 2020 at 23:27

Egor Skriptunoff

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