From: "Dan Stevens (IAmAI)" <dan.stevens.iamai@...>
Date: 2007-07-06T16:10:00+09:00
Subject: Re: Calling an arbitrary method as and when an array's contents change

I contemplated using the #hash method to determine if the array had changed:

[snip]

  def method_missing(meth, *args, &block)
    @last_hash = @array.hash
    @array.send(meth, *args, &block)
    if @array.hash != @last_hash
      changed
      notify_observers(@array, meth, *args, &block)
    end
  end

[snip]

That way I don't have to worry about which methods change the contents
of the array.

On 06/07/07, James Edward Gray II <james@grayproductions.net> wrote:
> 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
>
>