Often called cascading menu, a submenu is a secondary menu displayed within a MenuItem when the user clicks on it.
MenuItem.submenu readwrite property
Get or set the MenuItem submenu, a Menu object.
A nil value indicate that the MenuItem has no submenu.
Example
local ui = require "ui"
-- create a simple Window
local win = ui.Window("MenuItem.submenu sample", "fixed", 320, 250)
win.menu = ui.Menu()
-- Add a File menu
local File = win.menu:add("File", ui.Menu("New", "Open", "Reopen","Save", "Quit")).submenu
-- Assign a submenu to the third item "Reopen"
File.items[3].submenu = ui.Menu("sample1.lua", "sample2.lua", "sample3.lua")
win:show()
-- update user interface
repeat
ui.update()
until not win.visible