Objects

Objects are just tables.

All following 3 examples achieve the same effect.

Dog = {
    new = function (self, args)
        -- does something
    end
}

Dog = {}
function Dog.new(self, args)
    -- does something
end

Dog = {}
function Dog:new(args)
    -- does something
end

Now we will define how new() should work

function Dog:new()                         
    newObj = {sound = 'woof'}                
    self.__index = self
    return setmetatable(newObj, self)
end

The new() should return an instance which is a table (an object).
This table is returned by setmetatable()

return setmetatable(newObj, self)

which sets self as meta table for NewObj (the data for the instance or instance in itself but only from the definition perspective).

newObj = {sound = 'woof'}                

This allows us to overload the . operator which we do by

self.__index = self