Pitfalls & Anti-Patterns¶

local spellInfo = C_Spell.GetSpellInfo(116)  -- Returns a SpellInfo table or nil
if spellInfo then
    print("Spell:", spellInfo.name, "Icon:", spellInfo.iconID)
    -- Available fields: name, iconID, originalIconID, castTime, minRange, maxRange, spellID, spellSubtext
end

local itemInfo = C_Item.GetItemInfo(19019)  -- Returns an ItemInfo table or nil
if itemInfo then
    print(itemInfo.itemName .. " is quality " .. itemInfo.itemQuality)
end

local addonName, ns = ...

local frame = CreateFrame("Frame")
frame:RegisterEvent("ADDON_LOADED")
frame:SetScript("OnEvent", function(self, event, loadedAddon)
    if loadedAddon ~= addonName then return end
    self:UnregisterEvent("ADDON_LOADED")

    -- NOW SavedVariables are available
    MyAddonDB = MyAddonDB or {}
    MyAddonDB.settings = MyAddonDB.settings or { enabled = true }

    ns.db = MyAddonDB  -- Store reference in namespace for other files
end)

local addonName, ns = ...

local frame = CreateFrame("Frame")

ns.db = {}
ns.settings = { scale = 1.0 }
ns.ADDON_VERSION = "1.0.0"

local function Initialize()
    -- File-local, no conflict possible
end

local function OnUpdate(self, elapsed)
    -- File-local
end

frame:SetScript("OnUpdate", OnUpdate)

local addonName, ns = ...

-- Multi-file sharing: all .lua files in your .toc share the ns table
-- File: Core.lua
ns.Core = {}
function ns.Core:Init()
    -- ...
end

-- File: Config.lua (loaded after Core.lua via .toc order)
ns.Config = {}
function ns.Config:Load()
    ns.Core:Init()  -- Access other files through the namespace
end

-- For time, use WoW APIs:
local timestamp = GetTime()          -- Game time in seconds (float)
local serverTime = GetServerTime()   -- Server epoch time
local dateInfo = C_DateAndTime.GetCurrentCalendarTime()

-- C_Timer.NewTimer returns a ticker object with a Cancel method
local timer = C_Timer.NewTimer(5, function()
    print("Delayed action")
end)

-- This works!
timer:Cancel()

-- For repeating timers, use C_Timer.NewTicker
local ticker = C_Timer.NewTicker(1, function()
    print("Every second")
end)

-- Stop repeating
ticker:Cancel()

local pendingActions = {}

local combatFrame = CreateFrame("Frame")
combatFrame:RegisterEvent("PLAYER_REGEN_ENABLED")
combatFrame:SetScript("OnEvent", function()
    for _, action in ipairs(pendingActions) do
        action()
    end
    wipe(pendingActions)
end)

function ns:ShowLootFrame(items)
    if InCombatLockdown() then
        table.insert(pendingActions, function() ns:ShowLootFrame(items) end)
        print("Will show after combat ends.")
        return
    end

    local frame = CreateFrame("Frame", "MyLootFrame", UIParent, "SecureHandlerBaseTemplate")
    frame:SetSize(300, 400)
    frame:Show()

    for i, item in ipairs(items) do
        local btn = CreateFrame("Button", nil, frame, "SecureActionButtonTemplate")
        btn:SetAttribute("type", "item")
        btn:SetAttribute("item", item)
    end
end

local addonName, ns = ...

local frame = CreateFrame("Frame")
local events = {}

function events:PLAYER_LOGIN()
    -- handle login
end

function events:PLAYER_ENTERING_WORLD(isInitialLogin, isReloadingUI)
    -- handle entering world
end

function events:ADDON_LOADED(loadedAddon)
    if loadedAddon ~= addonName then return end
    -- handle addon loaded
end

function events:UNIT_HEALTH(unit)
    -- handle health — O(1) dispatch, no chain of comparisons
end

function events:PLAYER_REGEN_ENABLED()
    -- handle leaving combat
end

function events:PLAYER_REGEN_DISABLED()
    -- handle entering combat
end

-- Auto-register all events in the table
for event in pairs(events) do
    frame:RegisterEvent(event)
end

frame:SetScript("OnEvent", function(self, event, ...)
    events[event](self, ...)
end)

local pos = { x = 0, y = 0 }
local colors = { 1.0, 0.5, 0.0 }
local units = { "player", "target", "focus" }

frame:SetScript("OnUpdate", function(self, elapsed)
    pos.x, pos.y = 0, 0          -- Reuse existing table
    colors[1], colors[2], colors[3] = 1.0, 0.5, 0.0

    for _, unit in ipairs(units) do  -- Reuse existing table
        -- process units
    end
end)

-- Skip pattern instead of goto
for i = 1, 10 do
    if i ~= 5 then
        print(i)
    end
end

-- Use bit library (WoW provides bit.band, bit.bor, bit.lshift, etc.)
local flags = bit.band(0xFF, 0x0F)
local shifted = bit.lshift(flags, 4)

-- Use math.floor for integer division
local half = math.floor(10 / 2)

-- Use setfenv for environment manipulation (Lua 5.1)
-- But note: setfenv taints execution, avoid if possible

-- Use string.len for byte length (no native UTF-8 support)
local len = string.len("hello")

-- 4-argument form: left, right, top, bottom (NOT left, top, right, bottom!)
texture:SetTexCoord(0.25, 0.50, 0.0, 0.5)
--                  left  right top  bottom

-- 8-argument form for arbitrary quads (ULx, ULy, LLx, LLy, URx, URy, LRx, LRy)
-- Upper-Left, Lower-Left, Upper-Right, Lower-Right
texture:SetTexCoord(
    0.25, 0.0,   -- Upper-left
    0.25, 0.5,   -- Lower-left
    0.50, 0.0,   -- Upper-right
    0.50, 0.5    -- Lower-right
)

frame:RegisterEvent("COMBAT_LOG_EVENT_UNFILTERED")
frame:SetScript("OnEvent", function(self, event)
    local timestamp, subevent, hideCaster, sourceGUID, sourceName,
          sourceFlags, sourceRaidFlags, destGUID, destName, destFlags,
          destRaidFlags, spellID, spellName, spellSchool,
          amount = CombatLogGetCurrentEventInfo()

    if subevent == "SPELL_DAMAGE" then
        print(sourceName .. " hit " .. destName .. " for " .. (amount or 0))
    end
end)

function ns:GetSpellInfoSafe(spellID, callback)
    local info = C_Spell.GetSpellInfo(spellID)
    if info then
        callback(info)
        return
    end

    -- Data not cached yet — request it and wait
    C_Spell.RequestLoadSpellData(spellID)

    local frame = CreateFrame("Frame")
    frame:RegisterEvent("SPELL_DATA_LOAD_RESULT")
    frame:SetScript("OnEvent", function(self, event, loadedSpellID, success)
        if loadedSpellID == spellID then
            self:UnregisterEvent("SPELL_DATA_LOAD_RESULT")
            if success then
                callback(C_Spell.GetSpellInfo(spellID))
            end
        end
    end)
end

-- Usage
ns:GetSpellInfoSafe(12345, function(info)
    print("Spell: " .. info.name)
end)

local tabs = {
    { name = "General", icon = "inv_misc_gear" },
    { name = "Combat", icon = "ability_warrior_charge" },
    { name = "Loot", icon = "inv_misc_coin_01" },
}

-- ipairs() guarantees 1, 2, 3 order
for index, tab in ipairs(tabs) do
    CreateTab(index, tab.name, tab.icon)  -- Always correct order
end

-- Option 1: Prefix frame names with your addon name
local frame = CreateFrame("Frame", "MyAddonMainFrame", UIParent)
local settings = CreateFrame("Frame", "MyAddonSettingsPanel", UIParent)

-- Option 2: Use nil for frames that don't need global names
-- (Most frames don't! Only name them if other addons or macros need access)
local frame = CreateFrame("Frame", nil, UIParent)
local button = CreateFrame("Button", nil, frame)

-- Option 3: If you need the frame in XML or macro /click, still prefix
local btn = CreateFrame("Button", "MyAddonToggleButton", UIParent, "SecureActionButtonTemplate")

local addonName, ns = ...

ns.combatQueue = {}

local combatFrame = CreateFrame("Frame")
combatFrame:RegisterEvent("PLAYER_REGEN_ENABLED")
combatFrame:SetScript("OnEvent", function()
    for _, fn in ipairs(ns.combatQueue) do
        fn()
    end
    wipe(ns.combatQueue)
end)

function ns:RunSecure(fn)
    if InCombatLockdown() then
        table.insert(ns.combatQueue, fn)
    else
        fn()
    end
end

-- Now use it everywhere you touch secure frames
function events:BAG_UPDATE()
    ns:RunSecure(function()
        MyAddonSecureButton:SetAttribute("macrotext", "/use " .. ns:GetBestPotion())
        MyAddonSecureButton:Show()
    end)
end

function events:PLAYER_TARGET_CHANGED()
    ns:RunSecure(function()
        if UnitExists("target") then
            MyAddonTargetFrame:Show()
        else
            MyAddonTargetFrame:Hide()
        end
    end)
end

local addonName, ns = ...

-- The SLASH_ variable suffix must EXACTLY match the SlashCmdList key
-- The key must be UPPERCASE
SLASH_MYADDON1 = "/myaddon"
SLASH_MYADDON2 = "/ma"  -- Optional: multiple aliases

SlashCmdList["MYADDON"] = function(msg)
    local cmd, rest = strsplit(" ", msg, 2)
    cmd = strlower(cmd or "")

    if cmd == "config" or cmd == "options" then
        ns:OpenOptions()
    elseif cmd == "reset" then
        ns:ResetSettings()
    else
        print("|cff00ff00MyAddon|r commands: /myaddon config | reset")
    end
end