Method Chaining Example with Lua

-- method chaining example with Lua
-- what is method chaining? http://en.wikipedia.org/wiki/Method_chaining
-- i think its funny that the quick example that I thought of to type here also turns out to be a similar example in that article!

----------------------------------------------------------------
-- just some object setup code                                --
-- an important thing to note is the returns in the functions --
----------------------------------------------------------------

local obj = {name='unknown', age='unknown', gender='unknown', __tostring = function(self) return 'Name: '..self.name..', Age: '..self.age..', Sex: '..self.gender end}

function new()
  return setmetatable(obj, obj)
end

function obj:setName(n)
  self.name = n
  return self -- you must return self, or it wont work
end

function obj:setAge(n)
  self.age = n
  return self -- you must return self, or it wont work
end

function obj:setGender(n)
  n:lower()
  if n ~= 'male' and n ~= 'female' then
    n = 'confused'
  end
  self.gender = n
  return self -- you must return self, or it wont work
end

---------------------------------
-- THE METHOD CHAINING EXAMPLE --
---------------------------------

-- create it
local p = new()
print(p)

-- method chaining on an already created object
p:setName('Bob'):setAge(21):setGender('male')
print(p)

-- method chaining and creation on the same line
local p2 = new():setName('Janet'):setAge(18):setGender('female')
print(p2)

-- a more readable method chaining
local p3 = new():setName('Jose')
                :setAge(34)
                :setGender('other')
print(p3)