gistfile1.rb

class Class
  def attr_accessor_with_history(attr_name)
    attr_name = attr_name.to_s   # make sure it's a string
    attr_reader attr_name        # create the attribute's getter
    attr_reader attr_name+"_history" # create bar_history getter
    class_eval %q{"def #{attr_name} = value
                      #{attr_name}_history = nil
                      #{attr_name}_history.push(value)}

  end
end

class Foo
  #attr_accessor_with_history :bar
  attr_reader :bar
  attr_writer :bar
end

f = Foo.new
f.bar = 1
f.bar = 2
puts f.bar


Return Output
[nil, 1, 2]