From: James Edward Gray II <james@...>
Date: 2007-07-06T08:59:20+09:00
Subject: Re: Calling an arbitrary method as and when an array's contents change

On Jul 5, 2007, at 6:04 PM, Dan Stevens (IAmAI) wrote:

>> For this purpose, it's probably better to wrap/delegate to Array  
>> than extend it.
>
> This is a potential solution - I could override all the methods of the
> Array class that I think modify the contents of the Array in a
> superclass, calling Observable#changed before/after calling the
> parent's method. However, what if I think there's one too many methods
> to be overriding or a forget to override one?

It's really not too much work:

#!/usr/bin/env ruby -wKU

require "observer"

class OArray
   instance_methods.each { |meth| undef_method(meth) unless meth =~ / 
\A__/ }

   include Observable

   def initialize(array)
     @array = array
   end

   def method_missing(meth, *args, &block)
     @array.send(meth, *args, &block)

     if %w{ []= clear concat delete delete_at
            delete_if fill pop push replace shift }.include? 
(meth.to_s) or
        meth.to_s[-1] == ?!
       changed
       notify_observers(@array, meth, *args, &block)
     end
   end
end

class Array
   def to_oarray
     OArray.new(self)
   end
end

observer = Object.new
class << observer
   def update(array, *call)
     puts "You called #{call.first} and the Array is now # 
{array.inspect}."
   end
end

observed = [1, 2, 3].to_oarray
observed.add_observer(observer)
observed[1]
observed[1] = "2"

__END__

James Edward Gray II