method_missing.rb

class Bar
  attr_reader :hash
  def method_missing(m, *args)
    if m.to_s =~ /((set|get)_(.+))/
      case $2
      when 'set'
        self.class.send(:define_method,$1, lambda {|value| @hash ||= {}; @hash[$3] = value})
        send($1, args[0])
      when 'get'
        self.class.send(:define_method,$1, lambda {@hash ||= {};  @hash[$3]})
        send($1)
      end
    else
      super
    end
  end 
end

b = Bar.new
b.set_whateva "dude!!"
puts b.get_whateva