Manager

ball.lua

-- Possible topic:
-- - The require statement
local Manager = require 'manager'

-- Possible topic:
-- - Object-oriented programming
local Ball = Class{}
function Ball:init(x, y, r)
  self.x = x
  self.y = y
  self.r = r

  self.vx = math.random(50, 100)
  self.vy = math.random(50, 100)

  Manager.add(self)
end

function Ball:update(dt)
  if not (0 < self.x and self.x < love.graphics.getWidth()) then
    self.vx = -self.vx
  end

  if not (0 < self.y and self.y < love.graphics.getHeight()) then
    self.vy = -self.vy
  end

  self.x = self.x + (self.vx * dt)
  self.y = self.y + (self.vy * dt)
end

function Ball:draw()
  love.graphics.setColor(0, 255, 0)
  love.graphics.circle('fill', self.x, self.y, self.r)
end

return Ball

main.lua

Class = require 'class'

local Manager = require 'manager'
local Ball = require 'ball'
local Paddle = require 'paddle'

function love.load()
  for i = 1, 100 do
    Ball(
      math.random(love.graphics.getWidth()),
      math.random(love.graphics.getHeight()),
      math.random(5, 10))
    Paddle(
      math.random(love.graphics.getWidth()),
      math.random(love.graphics.getHeight()),
      math.random(5, 10),
      math.random(5, 10))
  end
end

function love.update(dt)
  Manager.map('update', dt)
end

function love.draw()
  Manager.map('draw')
end

manager.lua

local _objects = {}

-- Possible topic:
-- - Runtime benefits of _objects[o] = true over table.insert(_objects, o)
local function add(o)
  _objects[o] = true
end

local function remove(o)
  _objects[o] = nil
end

-- Possible topic:
-- - The vararg
-- - v[f](v, ...) : Why did I do it this way?
local function map(f, ...)
  for v,_ in pairs(_objects) do
    if v[f] then v[f](v, ...) end
  end
end

-- Possible topic
-- - The module
return {
  add = add,
  remove = remove,
  map = map,
}

paddle.lua

local Manager = require 'manager'

local Paddle = Class{}
function Paddle:init(x, y, w, h)
  self.x = x
  self.y = y
  self.w = w
  self.h = h

  self.vy = math.random(50, 100)

  Manager.add(self)
end

function Paddle:update(dt)
  if not (0 < self.y and self.y < love.graphics.getHeight()) then
    self.vy = -self.vy
  end

  self.y = self.y + (self.vy * dt)
end

function Paddle:draw()
  love.graphics.setColor(255, 0, 0)
  love.graphics.rectangle('fill', self.x, self.y, self.w, self.h)
end

return Paddle