原型

-- ConcretePrototype
local Square = {}
Square.__index = Square

function Square.new(color)
  return setmetatable({color = color}, Square)
end

-- A new table with the same fields
-- and the same class
function Square:clone()
  local copy = {}
  for key, value in pairs(self) do
    copy[key] = value
  end
  return setmetatable(copy, getmetatable(self))
end

-- Client: makes shapes from a prototype
-- without naming its class
local function shape_maker(shape)
  return function()
    return shape:clone()
  end
end

local square = Square.new("Red")
local make_shape = shape_maker(square)
local square1 = make_shape()
local square2 = make_shape()
local same = square1 == square2
-- same = false

-- No copy at all: an empty table that reads
-- missing fields from the prototype
local linked =
  setmetatable({}, {__index = square})

-- It follows the prototype, a clone does not
square.color = "Blue"
-- linked.color = Blue
-- square1.color = Red

print("same = " .. tostring(same))
print("linked.color = " .. linked.color)
print("square1.color = " .. square1.color)