Question

I’ve got a Lua script that presents an interactive text menu for configuring the script before actually doing the work. There is a main_menu() function, which has options the user can select, each of which call a different submenu() function. Each of those different submenu() functions do their thing and then they go back to (they call) the main_menu() function. Finally, each function has a parameter of settings passed to it, which is a table of settings.

Things look like this:

local function submenu(settings)
    -- Get user input & change a settings{} table key accordingly
    main_menu(settings)
end

local function main_menu(settings)
    -- Present choices & get user input
    submenu(settings)
end

local settings={}
settings["foo"] = "bar"

main_menu(settings)

The problem is I’m getting attempt to call nil errors whenever (as far as I can tell) a function calls another function that is defined later on in the script. So if, as in the example above, I define submenu() and then main_menu(), main_menu() has no problem calling submenu(), but submenu() can’t call main_menu().

FWIW, this is being done in the ComputerCraft mod for Minecraft.

Answer 1

You could either do a local function with forward declaration like this:

local main_menu

local function submenu(settings)
    -- Get user input & change a settings{} table key accordingly
    main_menu(settings)
end

main_menu = function(settings)
    -- Present choices & get user input
    submenu(settings)
end

or do a global function declaration by removing local keywords:

function submenu(settings)
    -- Get user input & change a settings{} table key accordingly
    main_menu(settings)
end

function main_menu(settings)
    -- Present choices & get user input
    submenu(settings)
end