错误 main.lua:23：尝试索引 upvalue 'Menu' （布尔值）

我正在尝试用 lua 和 love2d 制作一个主菜单，这是我第一次这样做，遗憾的是没有关于此事的教程，所以我自己尝试了一下。我一直遇到这个错误，我不知道如何解决它，请帮助！

完整错误消息： 错误main.lua：23：尝试索引upvalue“菜单”（布尔值）回溯main.lua：23：在函数“load”中[C]：在函数“xpcall”中[C]：在函数“xpcall”中

菜单文件

local Menu = {}
local game_state = 'menu'
local menus = { 'Play', 'Quit' }
local selected_menu_item = 1
local window_width
local window_height
local font_height

local Map = require("map")

-- functions
local draw_menu
local menu_keypressed
local draw_game
local game_keypressed

function Menu:load()

  -- get the width and height of the game window in order to center menu items
  self.window_width, self.window_height = love.graphics.getDimensions()

  -- use a big font for the menu
  self.font = love.graphics.newFont("assets/bit.ttf", 36)

  -- get the height of the font to help calculate vertical positions of menu items
  self.font_height = font:getHeight()

end

function Menu:update(dt)

end

function Menu:draw()
  local horizontal_center = self.window_width / 2
  local vertical_center = self.window_height / 2
  local start_y = vertical_center - (self.font_height * (#menus / 2))

  -- draw guides to help check if menu items are centered, can remove later
  -- love.graphics.setColor(1, 1, 1, 0.1)
  -- love.graphics.line(horizontal_center, 0, horizontal_center, window_height)
  -- love.graphics.line(0, vertical_center, window_width, vertical_center)

  -- draw game title
  love.graphics.setColor(1, 1, 1, 1)
  love.graphics.printf("Breakout", 0, 150, window_width, 'center')

  -- draw menu items
  for i = 1, #menus do

    -- currently selected menu item is yellow
    if i == selected_menu_item then
      love.graphics.setColor(1, 1, 0, 1)

    -- other menu items are white
    else
      love.graphics.setColor(1, 1, 1, 1)
    end

    -- draw this menu item centered
    love.graphics.printf(menus[i], 0, start_y + self.font_height * (i-1), self.window_width, 'center')

  end

end

function Menu:keypressed(key)

  -- pressing Esc on the main menu quits the game
  if key == 'escape' then
    love.event.quit()

  -- pressing up selects the previous menu item, wrapping to the bottom if necessary
  elseif key == 'up' then

    selected_menu_item = selected_menu_item - 1

    if selected_menu_item < 1 then
      selected_menu_item = #menus
    end

  -- pressing down selects the next menu item, wrapping to the top if necessary
  elseif key == 'down' then

    selected_menu_item = selected_menu_item + 1

    if selected_menu_item > #menus then
      selected_menu_item = 1
    end

  -- pressing enter changes the game state (or quits the game)
  elseif key == 'return' or key == 'kpenter' then

    if menus[selected_menu_item] == 'Play' then
      Map:load()
    elseif menus[selected_menu_item] == 'Quit' then
      love.event.quit()
    end

  end

end

主文件

love.graphics.setDefaultFilter("nearest", "nearest")
local Player = require("player")
local Coin = require("coin")
local GUI = require("gui")
local Spike = require("spike")
local Camera = require("camera")
local Stone = require("stone")
local Enemy = require("enemy")
local Map = require("map")
local Enemy2 = require("enemy2")
local Sound = require("sound")
local Menu = require("menu")

function love.load()
    Sound:init("music", "sfx/music.wav", "static")
    Sound:init("breeze", "sfx/breeze.mp3", "static")
    Enemy.loadAssets()
    Enemy2.loadAssets()
    Map:load()
    background = love.graphics.newImage("assets/background2.png")
    Player:load()
    GUI:load()
    Menu:load()
end

function love.update(dt)
    Sound:update()
    World:update(dt)
    Player:update(dt)
    Coin.updateAll(dt)
    Stone.updateAll(dt)
    Enemy.updateAll(dt)
    Enemy2.updateAll(dt)
    GUI:load(dt)
    Spike:updateAll(dt)
    Camera:setPosition(Player.x, 0)
    Map:update(dt)
    Menu:load()
end

function love.draw()
    love.graphics.draw(background)
    Map.level:draw(-Camera.x, -Camera.y, Camera.scale, Camera.scale)

    Menu:draw()
    Camera:apply()
    Player:draw()
    Enemy.drawAll()
    Enemy2.drawAll()
    Coin.drawAll()
    Spike.drawAll()
    Stone.drawAll()
    Camera:clear()

    GUI:draw()
end

function love.playmusic()
    loopingMusic = Sound:play("music", "sfx", 0.05, 1)
    loopingMusic:setLooping(true)
end

function love.playBreeze()
    loopingBreeze = Sound:play("breeze", "sfx", 0.3, 1)
    loopingBreeze:setLooping(true)
end

function love.keypressed(key)
    Player:jump(key)
    Menu:keypressed(key)
    if key == "m" then
        Sound:stop("sfx")
    end
end

function beginContact(a, b, collision)
    if Coin.beginContact(a, b, collision) then 
        return
    end
    if Spike.beginContact(a, b, collision) then 
        return end
    Enemy.beginContact(a, b, collision)
    Enemy2.beginContact(a, b, collision)
    Player:beginContact(a, b, collision)
end

function endContact(a, b, collision)
    Player:endContact(a, b, collision)
end

function endGame()
    love.event.quit()
end

您的 menu.lua 不会返回您的表菜单。

所以协助menu = require("menu")导致menu指的是Menu but to true.

来自Lua手册 http://www.lua.org/manual/5.4/manual.html#pdf-requirel:

一旦找到加载器，require就会用一个单一的调用调用加载器 参数，模组名称。如果加载器返回任何值，则需要分配 package.loaded[modname] 的返回值。如果装载机返回 没有值并且没有为 package.loaded[modname] 分配任何值， 然后 require 为该条目分配 true。无论如何，要求 返回 package.loaded[modname] 的最终值。

因此，在 main.lua 的第 23 行中，您实际上是在尝试索引 true（一个布尔值）。Menu:load()

Add return Menu到 menu.lua 的末尾