From: Payton Swick <payton@...>
Date: 2006-02-02T22:34:54+09:00
Subject: Re: callbacks, events, notification in general

Usage, by the way:

class A
   include HandlesEvents
end

a = A.new
a.on_event(:hello, :hi) { puts "Hello world!" }
a.handle(:hello)  # => prints "Hello world!"

-Payton

Payton Swick wrote:
> Not sure if it's any help, but here's something I've been using in my 
> code which is sort of the reverse of Observable.
> 
> This is actually just a snippet of the whole thing without comments or 
> some fancy features I added.  I may put it up as a gem if there's interest.
> 
> module HandlesEvents
>   attr_reader :handlers
> 
>   def on_event(*triggers, &handler)
>     @handlers ||= Hash.new
>     triggers.each { |trigger| @handlers[trigger] = handler }
>   end
> 
>   def handles?(trigger)
>     @handlers ||= Hash.new
>     return true unless @handlers[trigger].nil?
>     false
>   end
> 
>   def handle(trigger)
>     @handlers ||= Hash.new
>     @handlers[trigger].call(trigger) unless @handlers[trigger].nil?
>   end
> end
> 
> -Payton
> 
> 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.-