Elegant command-parsing in an OOP-based text game

Question

I\'m playing with writing a MUD/text adventure (please don\'t laugh) in Ruby. Can anyone give me any pointers towards an elegant, oop-based solution to parsing input text? <

Answer 1

For command interpreters, I'm rather fond of this simple, not all that elegant pattern. Patterns in dynamic languages tend to involve fewer boxes and lines than GOF patterns.

class Thing

  # Handle a command by calling the method "cmd_" + command.
  # Raise BadCommand exception if there is no method for that command.

  def handle_command(command, args)
    method_name = "cmd_#{command}"
    raise BadCommand, command unless respond_to?(method_name)
    send(method_name, args)
  end

  def cmd_quit(args)
    # the code for command "quit"
  end

  def cmd_list(args)
    # the code for command "list"
  end

  ...

end

In this way, adding a new command is just adding a new method. No tables or case statements need to be adjusted.