lua Error : attempt to call global 'Class' (a boolean value) - lua

Question

I am new to lua language .I have downloaded a class.lua file from github. I wrote a code for game developement by making classes in lua with love2d framework.I was making a pong game that needs paddles and ball,but it is giving me error like this:
Error
Ball.lua:2: attempt to call global 'Class' (a boolean value)
Traceback
Ball.lua:2: in main chunk
[C]: in function 'require'
main.lua:6: in main chunk
[C]: in function 'require'
[C]: in function 'xpcall'
[C]: in function 'xpcall'
I have spent so much time on it to solve but nothing happens.
main.lua
code is:
push =require 'push'
Class=require 'class'
require "Ball"
require "Paddle"
WINDOW_WIDTH=1280
WINDOW_HEIGHT=720
VIRTUAL_WIDTH=432
VIRTUAL_HEIGHT=243
--speed at which we will move our paddles; multiplied by dt in update
PADDLE_SPEED=200
function love.load()
love.graphics.setDefaultFilter('nearest','nearest')
--more 'retro-looking' font object we can use for any text
--os.time() give the time from 1 jan 1970
math.randomseed(os.time())
smallFont=love.graphics.newFont('font.ttf',8)
--set love2d active font to the small font object
scoreFont=love.graphics.newFont('font.ttf' , 32)
--larger font for drawing the score on the screen
love.graphics.setFont(smallFont)
--initialize window with virtual resolution
push:setupScreen(VIRTUAL_WIDTH,VIRTUAL_HEIGHT,WINDOW_WIDTH,WINDOW_HEIGHT,{
fullscreen=false,
resizable=false,
vsync=true
})
--Paddle(x,y,width,height)
player1=Paddle(10,30,5,20)
player2=Paddle(VIRTUAL_WIDTH-10,VIRTUAL_HEIGHT-30,5,20)
--place a ball in the middle of the screen
ball=Ball(VIRTUAL_WIDTH/2-2,VIRTUAL_HEIGHT/2-2,4,4)
gameState='start'
end
function love.update(dt)
--player 1 movement
if love.keyboard.isDown('w') then
--add negative paddle speed to current Y scaled by deltaTime
player1.dy=-PADDLE_SPEED
--player1Y= math.max ( 0, player1Y + -PADDLE_SPEED * dt)
elseif love.keyboard.isDown('s') then
--add positive paddle speed to current Y scaled by deltaTime
player1.dy=PADDLE_SPEED
else
player.dy=0
--player1Y = math.min ( VIRTUAL_HEIGHT -20 , player1Y + PADDLE_SPEED * dt)
end
--player 2 movement
if love.keyboard.isDown('up') then
--add negative paddle speed to current Y scaled by deltaTime
player2.dy=-PADDLE_SPEED
--player2Y=math.max( 0, player2Y + -PADDLE_SPEED * dt)
elseif love.keyboard.isDown('down') then
player2.dy=PADDLE_SPEED
else
player2.dy=0
end
if gameState=='play' then
ball:update(dt)
end
player1:update(dt)
player2:update(dt)
end
function love.keypressed(key)
--key can be acessed by sting name
if key=='escape' then
--function love give us to terminate application
love.event.quit()
elseif key == 'enter' or key == 'return' then
if gameState == 'start' then
gameState = 'play'
else
gameState = 'start'
ball:reset()
end
end
end
function love.draw()
--begin rendering at virtual screen
push:apply('start')
--recent versions of pong has grey color it sets grey color
love.graphics.clear( 0 , 0 , 0 , 255)
--note we are now using virtual width and height now for text placement
--draw welcome text on top of the screen
love.graphics.setFont(smallFont)
if gameState == 'start' then
love.graphics.printf('hello start state!', 0 , 20 , VIRTUAL_WIDTH , 'center' )
else
love.graphics.printf('hello play state!', 0 , 20 , VIRTUAL_WIDTH , 'center')
end
love.graphics.setFont(scoreFont)
love.graphics.print(tostring(player1Score),VIRTUAL_WIDTH / 2 - 50 , VIRTUAL_HEIGHT / 3)
love.graphics.print(tostring(player2Score),VIRTUAL_WIDTH / 2 + 30 , VIRTUAL_HEIGHT / 3)
player1:render()
player2:render()
ball:render()
--end rendering at virtual resolution
push:apply('end')
end
Ball.lua
code is:
--making a Ball class
Ball = Class{}
function Ball:init(x,y,width,height)
self.x=x
self.y=y
self.width=width
self.height=height
self.dy=math.random(2) ==1 and -100 or 100
self.dx=math.random(-50,50)
end
--[[places the ball in the middle of the screen with an
initial random velocity on both axes.]]
function Ball:reset()
self.x=VIRTUAL_WIDTH/2-2
self.y=VIRTUAL_HEIGHT/2-2
self.dy=math.random(2) == 1 and -100 or 100
self.dx=math.random(-50,50)
end
function Ball:update(dt)
self.x=self.x+self.dx * dt
self.y=self.y+self.dy * dt
end
function Ball:render()
love.graphics.rectangle('fill',self.x,self.y,self.width,self.height)
end
return Ball
plz help me on this matter.
Thanks in advance.

Answer 1

I had the same problem with the same CS50 course. I first had:
Class = require 'class'
push = require 'push'
require 'Ball'
require 'Paddle'
in main.lua and:
Paddle = class{}
in Paddle.lua.
I solved it by changing:
Class = require 'class'
to
require 'class'
and
Paddle = class{}
to
Paddle = class()
I had to read the readme from the class.lua library to figure it out.

Answer 2

Seems like you are on the tracks of the cs50 online course, I was having the same situation.
When I downloaded the distribution code, I saw that the class.lua file is not empty. When I changed the class.lua file with the file I have in my folder, problem was seemed to be solved.
Download the distribution code here