From: "Jack, Paul" <pjack@...>
Date: 2004-12-16T05:08:16+09:00
Subject: Can I make a new function like attr_accessor?

I'm writing a program that has a bunch of components I'd like
to link together using Java-style property change events.

So I created a mixin module:

  module Emitter

    def addListener(listener)
      @listeners.push(listener)
    end

    def removeLister(listener)
      @listeners.delete(listener)
    end

    def emit(sym, oldValue)
      @listeners.each { |x| x.propertyChanged(self, sym, oldValue) }
    end

  end

In my component objects, I just make them include Emitter and invoke
"emit" on any mutator:

  class ExampleComponent

    include Emitter

    def foo
      @foo
    end

    def foo=(x)
      old = @foo
      @foo = x
      emit(:foo, old)
    end

  end

I'd like to automate the creation of emitter properties, though.  Just
like I can use attr_accessor to quickly create readable/writeable 
attributes, I'd like a new attr_emitter function to quickly create 
readable/writeable/emitable attributes.

But I can't figure out how to do that. :(  Is it possible?  It would
save me a LOT of redundant typing...

Thanks all,

-Paul