Don't understand what is wrong with this class definition

[MrRalgoman]

I am following the gmod wiki and the default lua class definition style like so,
-- Inventory class
Inventory = { }
Inventory.__index = Inventory

--[[
Constructor

Args: Number fillCount, Number rows, Number cols
Desc: Creates a new inventory class
Return: Inventory
]]
function Inventory:New( fillCount, rows, cols )
    local this = { } 
    AccessorFunc( this, 'fillcount', 'FillCount', FORCE_NUMBER )
    AccessorFunc( this, 'rows', 'RowCount', FORCE_NUMBER )
    AccessorFunc( this, 'cols', 'ColumnCount', FORCE_NUMBER )
    this.fillcount = fillCount or 0
    this.rows = rows or 2
    this.cols = cols or 6

    for r = 1, this.rows do
        this[r] = { }
        for c = 1, this.cols do
            this[r][c] = InvenSlot:New( '', '', 0 ) end
    end

    setmetatable( this, Inventory )
    return this
end

--[[
Desc: Finds the next empty slot in the inventory
Return: Number row, Number column ( false if full )
]]
function Inventory:FindNextEmptySlot()
    for r = 1, self.rows do
        for c = 1, self.cols do
            if ( self[r][c]:GetItemCount() <= 0 ) then
                return r, c end
        end
    end

    return false
end

--[[
Args: String classname, Number count
Desc: Creates and inserts a new slot into the inventory
]]
function Inventory:Insert( classname, count )
    local r, c = self:Contains( classname )

    if ( r ) then
        self[r][c]:IncrementCount()
    else
        r = Inventory:FindNextEmptySlot()
        if ( not r ) then LocalPlayer():ChatPrint( 'Inventory full' ) return end

        local imagePath = 'materials/entities/' .. classname .. '.png'
        self[r][c]:SetClass( classname )
        self[r][c]:SetImage( imagePath )
        self[r][c]:SetItemCount( count )
    end
end

setmetatable( Inventory, { __call = Inventory.New } )

Creating an instance and calling insert:
local inven = Inventory( 0 )
inven:Insert( 'fart', 1 )

Calling insert creates an error in the FindNextEmptySlot method: (self.rows is nil for some reason?)
[ERROR] gamemodes/greyrp/gamemode/modules/inventory/client/c_inven.lua:36: 'for' limit must be a number
  1. FindNextEmptySlot - gamemodes/greyrp/gamemode/modules/inventory/client/c_inven.lua:36
   2. Insert - gamemodes/greyrp/gamemode/modules/inventory/client/c_inven.lua:72
    3. unknown - gamemodes/greyrp/gamemode/modules/inventory/client/inventory.lua:10
     4. include - [C]:-1
      5. unknown - gamemodes/greyrp/gamemode/modules/inventory/init.lua:23
       6. include - [C]:-1
        7. unknown - gamemodes/greyrp/gamemode/cl_init.lua:14

However, when I PrintTable( inven ) it shows that .rows = 2 and .cols = 6 as intended...

[bigdogmat]

You're calling `Inventory:FindNextEmptySlot()` instead of `self:FindNextEmptySlot()`

[MrRalgoman]

Damn, can't believe I missed that, thanks. What do you mean by doing the accessorfuncs on the meta table?

[Spar]

You made AccesorFunc on this table. Do this on Inventory