gistfile1.rb

class Statter
  
  def initialize
    @stat_calcuations = {}
    @results = {}
  end
  
  def stat_calcuation(name, args, &block)
    @stat_calcuations[name] = StatCalculation.new(name, args, block)
  end
  
  def update(name, args)
    stat = @stat_calcuations[name]
    key = stat.key_for_args(args)
    result = stat.get_result(args)
    @results[key] = result
  end
  
  def updated?(name, args, since)
    result = get_result(name, args)
    return result.last_updated > since
  end
  
  def get(name, args)
    result = get_result(name, args)
    result ? result.value : nil
  end
  
  def get_result(name, args)
    @results[StatCalculation.key_for_name_and_args(name, args)]
  end
  
  class StatCalculation < Struct.new(:name, :args, :block)
    def StatCalculation.key_for_name_and_args(name, args)
      "#{name}_#{args.join(':')}"
    end
    def key_for_args(args)
      StatCalculation.key_for_name_and_args(name, args)
    end
    def get_result(args)
      Result.new(key_for_args(args), self.block.call(args), Time.now)
    end
  end
  
  class Result < Struct.new(:key, :value, :last_updated)
  end

end


statter = Statter.new

statter.stat_calcuation :multiply, [:a, :b] do |a,b|
  a * b
end

puts "multiply 2x10? #{statter.get(:multiply, [2,10])} (not set yet)"

statter.update(:multiply, [2,10])

puts "multiply 2x10? #{statter.get(:multiply, [2,10])}"

last_check = Time.now

puts "anything new for multiply 2x10? #{statter.updated?(:multiply, [2,10], last_check)}"

statter.update(:multiply, [2,10])

puts "anything new for multiply 2x10? #{statter.updated?(:multiply, [2,10], last_check)}"