From: Wyss Clemens <WYS@...>
Date: 2001-12-06T23:41:53+09:00
Subject: [ruby-talk:27685] RE:  Emulating multimethods

> I want to write a class that emulates a piece of hardware.  The
> hardware spec I'm working from says that the Hardware reacts to
> different Inputs differently, depending on its State.

if your state doesn't change on every call(which I hope for you ;-)) the
"state-pattern" might help you here. At least to handle the "depending on
its State"-problem:
---------
class HardwareState
 def handle_input(input) 
  ...<put code here which every handle_input method does>
 end
end

class SleepingState < HardwareState
 def handle_input(input)
  ...
  super(input)
 end
end

..<the other HardwareState classes >

class Hardware
  def initialize(initialStateName = 'Sleeping')
    switch_to_state(initialStateName)
  end	

  def switch_to_state(stateName)	
    @state = Kernel.const_get((stateName + 'State').intern()).new()
  end

  def handle_input(input)
    @state.handle_input(input)
  end
end

hw = Hardware.new('Sleeping')
...
hw.handle_input(something)
...
hw.handle_input(somethingElse)
...
hw.switch_to_state('Happy')
...
hw.handle_input(something)
--------------

Regards
Clemens