From: John Johnson <johnatl@...>
Date: 2006-07-18T04:07:07+09:00
Subject: [Fwd: Re: Preferred monkeypatching technique]


> Daniel Berger wrote:

> Well, the idea is that the 3rd party software is going to be using
> whatever classes it has always used, so just creating a subclass doesn't
> get me anywhere because the 3rd party app (i.e. Rails) doesn't give a
> hoot about my BigNozzleFiretruck.

You could use a factory for that, and allow the plugin to override the
factory's creater method.

#!/usr/bin/env ruby

class FireTruck
  def say
    puts "truck"
  end
end

class FireTruckFactory
  def FireTruckFactory.create
    return FireTruck.new
  end
end

# First plugin
class Pumper < FireTruck
  def say
    puts "Pumper here."
  end
end

class FireTruckFactory
  def FireTruckFactory.create
    return Pumper.new
  end
end

# Second plugin
class HookAndLadder < FireTruck
  def say
    puts "Hook and ladder here."
  end
end

class FireTruckFactory
  def FireTruckFactory.create
    return HookAndLadder.new
  end
end

#try it
ft = FireTruckFactory.create
ft.say  # => Hook and ladder here.

Regards,
  JJ