[millanzarreta]

Ohh, that code looks nice... Can I modify it to not use the TrackerMeta object directly as data store? Can I use the TrackerMeta to store only the addon name (and the functions) and use this addon name to access a local variables when I wants?

I can't test this now, but I am looking some like this (modified version of your code):

--[[    Library Registration    ]]
local LibTalentsTrack=LibStub:NewLibrary("LibTalentsTrack-1.0",1);
if not LibTalentsTrack then return; end
 
--[[    Internal Variables  ]]
local MasterList=setmetatable({},{__mode="v"});--   Generate table with weak values to let GarbageCollection take them as necessary
 
--[[    Tracker Object Metatable    ]]
local TrackerMeta={__index={}};
 
local libUnitsToTrack = {}          --accesed libUnitsToTrack[addonName][guid]
local libUnitsToDoSomething2 = {}   --accesed libUnitsToDoSomething2[addonName][guid]
local libUnitsToDoSomething3 = {}   --accesed libUnitsToDoSomething3[addonName][guid]
 
function TrackerMeta.__index:RegisterUnit(unit)
--  self is our tracker object table given to addons
    if UnitExists(unit) then
        local guid=UnitGUID(unit);--    Save by GUID to guarantee correct tracking
        local addonName = self["addonName"]
        libUnitsToTrack[addonName][guid] = {0, 0, 0} --my default data
    end
end
 
function TrackerMeta.__index:UnregisterUnit(unit)
--  self is our tracker object table given to addons
    if UnitExists(unit) then
        local addonName = self["addonName"]
        libUnitsToTrack[addonName][UnitGUID(unit)]=nil;-- Erase data
    end
end
 
function TrackerMeta.__index:UnregisterAllUnits(unit)
--  self is our tracker object table given to addons
    local addonName = self["addonName"]
    table.wipe(libUnitsToTrack[addonName]);-- Erase everything
end
 
--  Generates new tracker object for addons to use (if exists, return the current tracker for that addon)
function LibTalentsTrack:NewTracker(addonName)
    if addonName == nil then return end
    local existTracker=MasterList[addonName];
    if not existTracker then
        local tracker = setmetatable({},TrackerMeta);
        tracker["addonName"] = addonName
        MasterList[addonName]=tracker["addonName"]
        return tracker
    end
    return existTracker
end
 
function LibTalentsTrack:DeleteTracker(tracker)
    if tracker == nil then return end
    local addonName = tracker["addonName"]
    table.wipe(tracker)
    tracker = nil
    MasterList[addonName]=nil
end
 
--Do stuff without problems with MasterList and GarbageCollector

If this is possible, it's easy for me programming the rest of library and I can use infinity variables to store info (with your code my data it's limited to the TrackerMeta object). I could manage complicated think like MasterList only on NewTracker and DeleteTracker functions and forget about this in the rest of the code. On every function that I needs differentiation I only should use local addonName = self["addonName"] and no more complications by metatables and GarbageCollector. It's this possible?

Forgive me if I pretend do some in wrong way, but the use of metatables and metafunctions are difficult to undestand for me :S

And one more question... what it's the purpose for the MasterList? I know it's for GarbageCollection, but, I don't know why it's needed...

Seriously, thank you very much, your help is helping me a lot!