gistfile1.rb

# -*- coding: utf-8 -*-

class DataObj
  attr_accessor :score
  def initialize
    @score=0
  end
end

class SaveData
  attr_accessor :data
  def initialize(file_name)
    load(file_name)
  end

  def load(file_name)
    if File.exist?(file_name)
      @data = File.open(file_name, "rb"){|f| Marshal.load(f) } 
    else
      @data= DataObj.new()
    end
  end

  # 書き込み
  def save
    File.open("test.dat", "wb"){|f| Marshal.dump(@data, f) }
  end
end

save_data = SaveData.new("test.dat") #セーブデータの読み込み
print "#{save_data.data.score}¥n"

save_data.data.score +=  rand(10)
save_data.save