From: itsme213 <itsme213@...>
Date: 2004-12-16T05:42:15+09:00
Subject: Re: Can I make a new function like attr_accessor?

It may be useful to look at this Ruby version of property change connectors
 http://raa.ruby-lang.org/project/observable/0.3


"Jack, Paul" <pjack@sfaf.org> wrote in message
news:F4F2EBDF8C16D5118B6500508BD32B4D02F8E1AA@earth.sfaf.org...
> 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