[inDef]

Hi All,

I asked the question "What is LibStub?" in the wrong forum on accident. Since I asked that question, I went and did some research and actually figured it out myself.

I'd like to post here my findings/conclusions so that it may help other people who have the same question I did. If you see anything wrong here, please feel free to correct me.

The following block of code is the exact code of LibStub.lua with detailed explanations of everything that is happening. I use the addon "LibAddonMenu-1.0" as an example throughout these explanations...thanks to Seerah for unknowingly allowing me to use his addon as an example

-- LibStub is a simple "version control" stub of code that ensures you are using the latest
-- version of all libraries that are registered with it...including itself.
-- Example: Your ESO client is running 2 different add-ons and both of them use the
--          library "LibAddonMenu-1.0".  However, one of the add-ons uses minor version 2
--          and the other minor version 4.  LibStub will ensure that the latest version
--          (version 4) is used by both add-ons.
 
local LIBSTUB_MAJOR, LIBSTUB_MINOR = "LibStub", 1
 
-- the _G table is the Lua "environment" where all Global variables are stored.
-- The point of this statement is to see if "LibStub" already exists in memory,
-- or more specifically, was already loaded by another add-on unknown to your add-on.
-- If LibStub has not been loaded yet anywhere, _G[LIBSTUB_MAJOR] will return nil.
 
local LibStub = _G[LIBSTUB_MAJOR]
 
local strformat = string.format
if not LibStub or LibStub.minor < LIBSTUB_MINOR then
 
    --[[
        If you got here, either LibStub was undefined (nil) or the current LibStub in memory has a lesser
        minor revision number than this one.  Assuming LibStub was undefined since this is version 1,
        the following 3 lines create a table titled 'LibStub' which looks like:
        
        LibStub = {
            
            libs = {}
            minors = {}
            minor = 1
        
        }
        
        and sets the global variable "LibStub" equal to this table.  This global table is now the LibStub definition
        for ALL add-ons that use it.
        
        If a newer version of LibStub exists in an add-on somewhere, that version will get used instead since the global
        table "LibStub" will be set there.  
    --]]
 
    LibStub = LibStub or {libs = {}, minors = {} }
    _G[LIBSTUB_MAJOR] = LibStub
    LibStub.minor = LIBSTUB_MINOR
    
    
    -- Register a new library with LibStub
    function LibStub:NewLibrary(major, minor)
    
        assert(type(major) == "string", "Bad argument #2 to `NewLibrary' (string expected)")
        minor = assert(tonumber(zo_strmatch(minor, "%d+")), "Minor version must either be a number or contain a number.")
        
        -- Example:  major = "LibAddonMenu-1.0" and minor = 4
        
        -- oldminor = LibStub.minors["LibAddonMenu-1.0"]
        -- If a version of LibAddonMenu is already loaded into memory, oldminor will contain it's version number.
        -- Otherwise, oldminor = nil.
        local oldminor = self.minors[major]
        
        -- If a version of LibAddonMenu is already in memory AND it's version number is greater than or equal to
        -- the new library, exit the function and return nil.
        if oldminor and oldminor >= minor then return nil end
        
        -- If you got here, that means either this new library doesn't exist in memory or it's a newer version
        -- Set the minor version number of LibAddonMenu to 4.  If LibStud.libs["LibAddonMenu-1.0"] already exists,
        -- continue to use that library.  Otherwise, set to {}.
        -- LibStub.minors["LibAddonMenu-1.0"] = 4, LibStub.libs["LibAddonMenu-1.0"] = LibStub.libs["LibAddonMenu-1.0"] or {}
        self.minors[major], self.libs[major] = minor, self.libs[major] or {}
        
        -- Return the library table and the oldminor version number.
        -- If this is a brand new library (not in memory already) the library table will be empty. 
        return self.libs[major], oldminor
        
    end
    
    -- Grabs a library for you to use.  For example, if you want to use the LibAddonMenu-1.0 library
    -- you would call LAM = LibStub:GetLibrary("LibAddonMenu-1.0").  This returns all definitions
    -- of the library (methods, variables, tables, etc.) into your new object LAM.
    function LibStub:GetLibrary(major, silent)
        if not self.libs[major] and not silent then
            error(("Cannot find a library instance of %q."):strformat(tostring(major)), 2)
        end
        return self.libs[major], self.minors[major]
    end
    
    -- See all libraries currently registered with LibStub in memory
    function LibStub:IterateLibraries() return pairs(self.libs) end
    
    -- Allows a shortcut way to call the GetLibrary function.
    -- These two calls become 100% equivalent:
    --   LAM = LibStub:GetLibrary("LibAddonMenu-1.0")
    --   LAM = LibStub("LibAddonMenu-1.0")
    setmetatable(LibStub, { __call = LibStub.GetLibrary })
    
end

If you have any questions please feel free to ask!