Re: A function to create an object using closures

["Evan DeMond" <evan.demond@...>]

On Fri, Nov 21, 2008 at 6:26 AM, Michal Cizmazia <big.sea.cow@gmail.com> wrote:

-- What do you think about the following object-oriented approach,
-- in which a function is used to create an object using closures?
-- I am looking forward to your responses.
-- Michal Cizmazia

[snip]

Interesting, I never thought of that approach. I feel like it's a little complicated with the "self" pointers and getters for private members. Personally, I like to use a "prototype" sort of approach, using metatables:

function clone(obj) -- or "inherit", "extend", "derive", etc...
    local c = {}
    setmetatable(c, {__index = obj})
    return c
end

Greeting = {}
Greeting.message = "Good morning"

PersonalizedGreeting = clone(Greeting)
PersonalizedGreeting.name = "no name yet"

function Greeting.new()
    return clone(Greeting)
end

function Greeting:say()
    print (self.message)

end

function PersonalizedGreeting.new()
    return clone(PersonalizedGreeting)
end

function PersonalizedGreeting:setName(name)
    self.name = name
end

function PersonalizedGreeting:say()
    print(self.message .. " " .. self.name)
end

It's a bit wacky, I guess, in that clone() gets used to express both inheritance and instantiation. You create an object to serve as a class, then inherited classes just clone the first class and add/override things.