Why is the dictionary not working? it's literally 3 am ,and i'm sitting over this problem for an hour!

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1

I’m losing my mind, because i’m literally picking a value from the table and it returns me a nil,
even if i set a true value, right before picking the value and printing it, help!

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2

Apparently, GetCell(...).ToIterate doesn’t have those fields.

Saying ToIterate[X][Y] in the line before is unrelated, as that’s apparently a different. If you shared the whole code maybe it would be easier to help.

3

But i literally changed the index value above the same index value ,when printing it

4 
local function GetCell(X,Y,Table)
	if Table[X] then
		return Table[X][Y]
	end
end
ToIterate[Coords.X][Coords.Y] = true
print(GetCell(Coords.X,Coords.Y,FreeCells),ToIterate[Coords.X][Coords.Y])
5

There’s only (possible thing that could make a bug) a metatable, but it doesn’t matter

	setmetatable(ToIterate,{
		__index = function()
			return {}
		end,
	})
6

Where are you getting the values for Coords.X and Coords.Y?

7

Coords.X and Coords.Y are an integers, that’s all you need to know.
But if you truly want to know, that’s the whole function.

local function InsertToFreeCells(Table)
		for n = 1,#Table do
			local Coords = Table[n].Coordinates
			if not GetCell(Coords.X,Coords.Y,ToIterate) and not GetCell(Coords.X,Coords.Y,Paths) then
				table.insert(FreeCells,Table[n])
				ToIterate[Coords.X][Coords.Y] = true
				print(GetCell(Coords.X,Coords.Y,FreeCells),ToIterate[Coords.X][Coords.Y])
				FreeCells.length += 1
			end
		end
		return true
	end
8

This is the bug.

Or part of it anyways.

Saying ToIterate[X], if X doesn’t exist as a member, will trigger your meta method and return a new table {}. Critically though, __index will not set ToIterate[X] = {}. It just returns and leaves it, so when you do

ToIterate[X][Y] = true
-- or, equivalently:
local x = ToIterate[X]
x[Y] = true

And the first lookup fails, your meta table takes over so you end up doing

local x = {} -- because ToIterate[X] failed so __index returns this
x[Y] = true

And then when you print out ToIterate[X][Y], the lookup fails again (because __index doesn’t modify the table unless you tell it to) and tries to lookup Y on a new empty table.

All that’s to say that you probably want your metatable to do this:

__index = function(t, k)
  local new = {}
  rawset(t, k, new) -- t[k] = new but withou invoking this meta method again
  return new
end)
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