From: Robert Klemme <bob.news@...>
Date: 2006-02-02T06:56:20+09:00
Subject: Re: callbacks, events, notification in general

Damphyr wrote:
> OK, bare with me, this is brainstorming of a sorts:
> I want to have some kind of event notification from my classes.
> Typically what I would do would be to pass a logger object and let the
> class log by itself, but I'm not really satisfied with this solution
> in most cases.
>
> What I would prefer was define a callback method and give this to the
> object. Then I could do whatever I want with it and not only use logs.
> Mostly I want to have progress reports.
>
> something like
>
> class A
>    def set_callback notify
>      @notify=notify
>    end
>    def something
>      puts "something"
>      send(@notify) if @notify
>    end
> end
>
> def coocoo
> puts "hey"
> end
> a=A.new
> a.something
> a.set_callback(:coocoo)
> a.something
>
> Now this does exactly what I want and can be wrapped up in a module to
> be included for general use.
> Question: Is there a "better" solution? What are my alternatives?
> Cheers,
> V.-

I find usage of a symbol quite clumsy.  One of the drawbacks is that it
cannot address a single instance's method easily.  I'd use at least blocks
for this.  But why not simply use Observer?  It's the exact thing built
for this situation - and it's part of the std distribution.

http://www.ruby-doc.org/stdlib/libdoc/observer/rdoc/index.html

Kind regards

    robert