From: Jacob Fugal <lukfugl@...>
Date: 2005-07-19T23:18:45+09:00
Subject: Re: ] Re: Ruby has ruined my Java (was Re: Ruby has ruined my C++)

On 7/18/05, Daniel Amelang <daniel.amelang@gmail.com> wrote:
> So, tell my why you prefer the on_event( :event_type ) syntax?
> 
> I prefer the when_pushed syntax because of the readablity and
> abstraction of events altogether. 'button when pushed do this' feels
> very natural. But maybe it feels very unnatural for others. 'button on
> event push' is OK with me, it's the fxRuby way after all.
> 
> The when_pushed method would actually (via the magic of method missing
> possibly) translate to something like register_handler (:push, block)
> under the hood.

I don't know, it's just preference. :) Your syntax is a good
alternative. But I'll take a stab at explaining my preference
anyway...

I think the main difference is the conciseness of the grammar style,
and an easier reflection between event handling and event generation.
For one thing, the 'when_pushed' variant would need a translation in
method_missing to turn 'pushed' into :push. The 'on_*' route doesn't
necessarily preclude method_missing abstraction either:

module EventListener
  def register_handler( event_name, &action )
    @actions ||= {}
    @actions[event_name] ||= []
    @actions[event_name] << action
  end
  def handle_event( event_name )
    if @actions[event_name]
      @actions[event_name].each { |action| action[self] }
    end
  end
  def method_missing( symbol, *args, &block )
    if /^on_/.match( symbol )
      self.register_handler( symbol.to_s.gsub(/^on_/, '').to_sym, *args ) &block
    else
      self.handle_event( symbol )
    end
  end    
end

class Button
  include EventListener
end

button = Button.new
button.on_push do |b|
  puts "Don't push my buttons!"
end

button.push