From: David Masover <ninja@...>
Date: 2009-07-14T00:28:54+09:00
Subject: Re: Prototype-Based Inheritance (#214)

On Sunday 12 July 2009 12:49:55 pm lith wrote:

>     def prototype=(prototype)
>         merge!(prototype) {|k,o,n| o}

I based my implementation on Javascript, and one of the nice properties there 
is that the prototype can change later. So, for example, in my implementation:

irb(main):005:0> pele.favorite_food = 'hamburger'
=> "hamburger"
irb(main):006:0> pele_jr.favorite_food
=> "hamburger"
irb(main):007:0> pele
=> {:name=>"Pele", :sport=>"football", :position=>"Forward", 
:favorite_food=>"hamburger"}
irb(main):008:0> pele_jr.favorite_food = 'cheeseburger'
=> "cheeseburger"
irb(main):009:0> pele_jr.favorite_food
=> "cheeseburger"
irb(main):010:0> pele.favorite_food
=> "hamburger"

Of course, this is slower, but more powerful, I think.

>             when Proc
>                 return val.call(self, *args)
>             end
[snip]
> This would allow you to do something like:
>
> pele_jr.age = 20
> pele_jr.foo = lambda {|this, a| this.age + a}
> pele_jr.foo(10) #=> 30

Nice touch...

Here's mine:

module Prototype
  attr_accessor :prototype
  def method_missing *args
    prototype.public_send *args
  end
end

That's more generic than just hashes. Mix it into Object and it works on 
anything. Of course, it's not exactly convenient to have to define new values 
like this:

pele = Object.new
class << pele
  attr_accessor :name
end
pele.name = 'Pele'

It also severely limits what you can do with some of the builtin classes like 
Fixnums that can't have a metaclass.

And of course, to make it saner for the example (and because OpenStruct won't 
cooperate), I can do this:

class Hash
  include Prototype
  def method_missing name, *args
    if has_key? name
      self[name]
    elsif name =~ /.=$/
      self[name.to_s.chomp('=').to_sym] = args.first
    else
      super
    end
  end
end