Simple classes for Lua

class.lua

--[[
No-nonsense classes for Lua.

Basic usage:

  A = class() -- class declaration
  B = class(A) -- inheritance
  function A:init(arg, arg ...) -- constructor
  function A:foo(arg, arg ...) -- method declaration
  a = A(arg, arg ...) -- construction
  a:foo(arg, arg ...) -- method invocation
  
Setting properties:

  A = class()
  function A:init(x)
    self.x = x
  end
  ...
  a = A()
  print(a.x)

Overriding methods:

  B = class(A)
  ...
  function B:foo(a, b)
    A.foo(self, a, b)
    ...
  end
]]

local function construct(class, ...)
  local t = {}
  local mt = {}
  mt.__index = class
  setmetatable(t, mt)
  if class.init then
    class.init(t, ...)
  end
  return t
end

function class(base)
  local t = {}
  local mt = {__call = construct}
  if base then
    mt.__index = base
  end
  return setmetatable(t, mt)
end