From: Tim Waters <timgwaters@...>
Date: 2006-12-24T01:02:47+09:00
Subject: Help with a ruby idiom

From the O'Reilly Cookbook there is code that keeps call functions in a
hash as a subscriber/listener type pattern.  What I don't understand (or
I don't understand how it works is the line:
(@EventDispatcher_listeners[event] ||= []) << callback


module EventDispatcher
    def setup_listeners
    @EventDispatcher_listeners = {}
  end

  def subscribe(event, &callback)
    (@EventDispatcher_listeners[event] ||= []) << callback
  end

  protected
  def notify(event, *args)
    if @EventDispatcher_listeners[event]
      @EventDispatcher_listeners[event].each do |m|
        m.call(*args) if m.respond_to? :call
      end
    end
    return nil
  end
end

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