Saved variables not working

[Codger]

I've created a very simple addon to see how saved variables work but the saved variables are not working.
Here is what I have so far:

My .toc file:

## Title: MyAddon
## Interface: 100206
## Version: 1.0
## Author: 
## Notes: A simple WoW addon using a database
## SavedVariablesPerCharacter: MyAddonDb
MyAddon.lua

and my lua code is:

-- Create a saved variable to store last time
local lastLogoffTime = nil
 
-- Create a new frame
local frame = CreateFrame("Frame")
 
-- Load last logoff time from saved variable
local function LoadLastLogoffTime()
    if MyAddonDB then
        lastLogoffTime = MyAddonDB.lastLogoffTime
        print("Last logoff time loaded:", lastLogoffTime)
    else
        print("Trying to load logoff time but MyAddonDB is nil.")
    end
end
 
-- Save last time to saved variable
local function SaveLastLogoffTime(time)
    if not MyAddonDB then 
        print("Trying to save logoff time but MyAddonDB is nil") 
    else
        MyAddonDB.lastLogoffTime = time
    end
end
 
-- Hook the Logout event to update last logoff time
frame:RegisterEvent("PLAYER_LOGIN")
frame:RegisterEvent("PLAYER_LOGOUT")
frame:SetScript("OnEvent", function(self, event)
    if event == "PLAYER_LOGIN" then
        if not MyAddonDB then
            MyAddonDB = {}
            print ("MyAddonDB was nil")
        end
        LoadLastLogoffTime()
    elseif event == "PLAYER_LOGOUT" then
        SaveLastLogoffTime()
    end
end)
 
-- Slash command handler function
local function SlashCommandHandler(msg)
    LoadLastLogoffTime()
end
 
-- Register slash command
SLASH_MYADDON1 = "/myaddon"
SlashCmdList["MYADDON"] = SlashCommandHandler

When I login I see these messages:
My AddonDB was nil
Lastlogofftimeloaded: nil

and after logging out, the contents of the saved variable file 'MyAddon.lua' is:
MyAddonDb = nil

I've looked at so many posts but can't seem to figure out what I'm doing wrong.
I've logged out of my character and deleted the WTF saved variables file - didn't help.
I've restarted my computer in case the file was somehow preventing writing but no help.
I appreciate any help you can provide.

[Fizzlemizz]

MyAddonDB.lastLogoffTime = time

Should probably be

MyAddonDB.lastLogoffTime = time()

for the time function rather than a non-existant variable because you're not passing anything to SaveLastLogoffTime (and if you were it would just be time() presumably.

That and lua is case sensitive. MyAddonDb in the .toc is not the same as MyAddonDB in the code.

[Codger]

Thank you Fizzlemizz!!
I changed the time to a date function and renamed the db file in the toc.

Here is the final code, toc file first:

## Title: MyAddon
## Interface: 100206
## Version: 1.0
## Author: 
## Notes: A simple WoW addon using a database
## SavedVariablesPerCharacter: MyAddonDB
MyAddon.lua

-- Create a saved variable to store last time
local lastLogoffTime = nil
 
-- Create a new frame
local frame = CreateFrame("Frame")
 
-- Load last logoff time from saved variable
local function LoadLastLogoffTime()
    if MyAddonDB then
        lastLogoffTime = MyAddonDB.lastLogoffTime
        print("Last logoff time loaded:", lastLogoffTime)
    else
        print("Trying to load logoff time but MyAddonDB is nil.")
    end
end
 
-- Save last time to saved variable
local function SaveLastLogoffTime(time)
    if not MyAddonDB then 
        print("Trying to save logoff time but MyAddonDB is nil") 
    else
        MyAddonDB.lastLogoffTime = date("%m/%d/%y %H:%M:%S")
    end
end
 
-- Hook the Logout event to update last logoff time
frame:RegisterEvent("PLAYER_LOGIN")
frame:RegisterEvent("PLAYER_LOGOUT")
frame:SetScript("OnEvent", function(self, event)
    if event == "PLAYER_LOGIN" then
        if not MyAddonDB then
            MyAddonDB = {}
            print ("MyAddonDB was nil")
        end
        LoadLastLogoffTime()
    elseif event == "PLAYER_LOGOUT" then
        SaveLastLogoffTime()
    end
end)
 
-- Slash command handler function
local function SlashCommandHandler(msg)
    LoadLastLogoffTime()
end
 
-- Register slash command
SLASH_MYADDON1 = "/myaddon"
SlashCmdList["MYADDON"] = SlashCommandHandler

[Fizzlemizz]

Saving

MyAddonDB.lastLogoffTime = date("%m/%d/%y %H:%M:%S")

just saves a string of "03/23/24 03:03:38"

No very useful in future if you just want the date part or just the time part (having to slice up a string).
Probably better saving as

MyAddonDB.lastLogoffTime = date()

And you can do the formatting when you display whatever part(s).

[Fizzlemizz]

As an aside, all addons and the Blizzard UI share the same global table so any variable that will be global like frame names and SaveVariable names should be unique. Blizzard will use "common" names so addons should use things like prefixing with the addon name.

Saying this because MyAddonDB might be unknowingly used by any first time addon author that doesn't know.

[Codger]

Thank you Fizzlemizz. Those are both very good points and I appreciate your thoughtful replies.
This code has been modified to use a unique database name and a more generic form of the date function.
I might have overdone the db name a little bit, but it makes a good point.

Here is the saved variables toc file:

## Title: MyAddon
## Interface: 100206
## Version: 1.0
## Author: 
## Notes: A simple WoW addon using a database
## SavedVariablesPerCharacter: MyAddonDBExampleMarch2024 --must be unique
MyAddon.lua

Here is the saved variables lua file:

-- Create a saved variable to store last time
local lastLogoffTime = nil
 
-- Create a new frame
local frame = CreateFrame("Frame")
 
-- Load last logoff time from saved variable
local function LoadLastLogoffTime()
    if MyAddonDBExampleMarch2024 then
        lastLogoffTime = MyAddonDBExampleMarch2024.lastLogoffTime
        print("Last logoff time loaded:", lastLogoffTime)
    else
        print("Trying to load logoff time but MyAddonDBExampleMarch2024 is nil.")
    end
end
 
-- Save last time to saved variable
local function SaveLastLogoffTime()
    if not MyAddonDBExampleMarch2024 then 
        print("Trying to save logoff time but MyAddonDBExampleMarch2024 is nil") 
    else
        MyAddonDBExampleMarch2024.lastLogoffTime = date()
    end
end
 
-- Hook the Logout event to update last logoff time
frame:RegisterEvent("PLAYER_LOGIN")
frame:RegisterEvent("PLAYER_LOGOUT")
frame:SetScript("OnEvent", function(self, event)
    if event == "PLAYER_LOGIN" then
        if not MyAddonDBExampleMarch2024 then
            MyAddonDBExampleMarch2024 = {}
            print ("MyAddonDBExampleMarch2024 was nil")
        end
        LoadLastLogoffTime()
    elseif event == "PLAYER_LOGOUT" then
        SaveLastLogoffTime()
    end
end)
 
-- Slash command handler function
local function SlashCommandHandler(msg)
    LoadLastLogoffTime()
end
 
-- Register slash command
SLASH_MYADDON1 = "/myaddon"
SlashCmdList["MYADDON"] = SlashCommandHandler

One more question, if I had an extremely unique database name that was 50 or 60 characters long, how could I set up an alias?
Something like a local variable defined at the top and set in event PLAYER_LOGIN?

[Fizzlemizz]

After the gobal has been created you can alway do

local db = MyVeryLongGlobaVariableName

When using tables, making changes to the local eg.

db.SomeVariable = "SomeThing New"

Will change the entry in the MyVeryLongGlobaVariableName table.

With other simple types (strings, numbers etc.) changing the local variable won't change the global.

Global names don't have to be uber long, just unique. The addon (folder) name will always be unique (or acronym with something like _DATA after it.)

locals are scope restricted so a local defined in anything the ends with an END (if, function etc.) will only be available in that scope.

local a = 2
print(a) -- prints 2
if 1 == 1 then
    print(a) -- prints 2
    local a = 3
    print(a) -- prints 3
end
print(a) -- prints 2, back to original "scope"