serializable.rb

# a module to make insertions and updates serializable given the unique keys/fields 
# a unique constraint have to be created based the keys
module Serializable
  EXCEPTIONS = [
    ActiveRecord::StaleObjectError, ActiveRecord::StatementInvalid,
    ActiveRecord::RecordNotUnique 
  ]

  def self.included(base_class)
    base_class.extend(ClassMethods)
  end

  module ClassMethods
    def with(keys, &proc)
      object = where(keys).first || new(keys)
      proc.call(object)
      object.save!
    rescue *EXCEPTIONS 
      retry
    end 
  end
end