Cannot initialize my addon

[entr0py42]

Hi all,
I'm trying to get into creating addons. I'm working on an addon that displays the total value of the items you've picked.

No matter what I try, I cannot initialize it. I've tried several approaches and inspected a few addons to understand how they do it. I think the problem is OOP related.

The error I get:

user:/AddOns/SimpleFarmTrack/SimpleFarmTrack.lua:37: function expected instead of nil
stack traceback:
user:/AddOns/SimpleFarmTrack/SimpleFarmTrack.lua:37: in function '(anonymous)'

The code:

local ADDON_NAME = "SimpleFarmTrack"
SimpleFarmTrack = {}
local async = LibAsync
 
 
local function GetItemPrice(itemLink)
    local price = LibPrice.ItemLinkToPriceGold(itemLink)
    if (price == nil or price == 0) then price = GetItemLinkValue(itemLink, true) end
    return price
end
 
 
local total = 0
function SimpleFarmTrack:OnItemLoot(eventCode, name, itemLink, quantity)
  total = total + GetItemPrice(itemLink) * quantity
  SimpleFarmTrackLabel:SetText(string.format("%.2f",total))
end
 
function SimpleFarmTrack:AddEventHandlers()
  EVENT_MANAGER:RegisterForEvent(
    ADDON_NAME,
    EVENT_LOOT_RECEIVED,
    function(...)
      async:Call(self:OnItemLoot(...))
    end
  )
end
 
function SimpleFarmTrack:OnAddOnLoaded(event, addonName)
  if addonName == ADDON_NAME then self:AddEventHandlers() end
end
 
EVENT_MANAGER:RegisterForEvent(
    ADDON_NAME,
    EVENT_ADD_ON_LOADED,
    function(...)
      SimpleFarmTrack:OnAddOnLoaded(...)
    end
)

If I remove the entire EVENT_MANAGER part at the end and replace it with

SimpleFarmTrack:AddEventHandlers()

it works.