CSC/ECE 517 Fall 2007/wiki1b 7 c9

Question

Take a case of the Command pattern and implement it as succinctly as possible in Ruby and Java. Compare the two implementations in terms of clarity and succinctness. The example should be a "real-world" example. While it may be grossly oversimplified for the purpose of illustration, it should not be totally contrived (i.e., should not raise the question, Why would anyone ever want to do that?).

---

Ruby Implementation

class FireEmergencyButton
  def initialize(onCommands, offCommands)
    @onCommands = onCommands
    @offCommands = offCommands
  end
  def press
    @onCommands.each{|command| command.call}
  end
  def depress
    @offCommands.each{|command| command.call}
  end
end

waterSprayOnCommand  = proc{puts "Started spraying water!"}
waterSprayOffCommand  = proc {puts "Stopped spraying water..."}
fireAlarmOnCommand = proc{puts "Fire alarm is on!"}
fireAlarmOffCommand = proc {puts "Fire alarm is off..."}
fireStationCallCommand = proc{puts "Fire department is called!"}

onCommands = []
onCommands << fireAlarmOnCommand  
onCommands << waterSprayOnCommand
onCommands << fireStationCallCommand

offCommands = []
offCommands << fireAlarmOffCommand
offCommands << waterSprayOffCommand  

feb =FireEmergencyButton.new(onCommands, offCommands)
puts "Fire Emergency Button is pressed!"
feb.press
puts ""
puts "Fire Emergency Button is depressed!"
feb.depress