Simple dirty? flag

gistfile1.rb

class Percent
  attr_reader :finished
  attr_accessor :dirty

  def finished=(value)
    self.dirty = true
    @finished = value
  end

  def dirty?
    !!dirty
  end

  def initialize(attributes = {})
    self.finished = attributes[:finished] || 0
    self.dirty = false
  end
end

p = Percent.new(:finished => 10)

puts p.finished
#=> 10
puts p.dirty?
#=> false

p.finished = 20

puts p.finished
#=> 20
puts p.dirty?
#=> true