In-memory Software Transactions

gistfile1.rb

lass TransactionalHash < Hash
  def transaction
    old = dup
    begin 
      return tap { yield(self) }
    rescue Exception => e
      clear
      old.each do |k,v|
        self[k] = v
      end
      raise e
    end
  end
end

class Transaction 
  def self.start(obj)
    new(obj)
  end

  def assign_object(obj)
    @version = obj
    self
  end

  def initialize(obj)
    @version = obj
    @actions = []
  end

  def perform(&block)
    @actions << block
    self
  end

  def commit
    old = @version
    @actions.each do |a|
      @version = a.call(@version)
    end
    return @version
  rescue Exception => e
    @version = old
    raise e
  end
end