charlie.rb

## Example 3 ###

class Charlie

  def hey(drivel)
    answerer(drivel).reply
  end

  private

  def answerer(drivel)
    handlers.find {|answer| answer.handles?(drivel)}.new
  end

  def handlers
    [AnswerSilence, AnswerShout, AnswerQuestion, AnswerDefault]
  end

end

class AnswerSilence

  def self.handles?(input)
    input.nil? || input.empty?
  end

  def reply
    'Fine. Be that way!'
  end

end

class AnswerQuestion

  def self.handles?(input)
    input.end_with?('?')
  end

  def reply
    'Sure.'
  end

end

class AnswerShout

  def self.handles?(input)
    input == input.upcase
  end

  def reply
   'Woah, chill out!'
  end

end

class AnswerDefault

  def self.handles?(input)
    true
  end

  def reply
    'Whatever.'
  end

end