updated_at_locking.rb

module UpdatedAtLocking

  def self.included(base)
    base.alias_method_chain :update, :stale_object_detection
    base.class_inheritable_accessor :updated_at_locking_enabled, :instance_writer => false
    base.updated_at_locking_enabled = true
  end

  def updated_at_locking_enabled?
    self.updated_at_locking_enabled == true
  end

  ##
  # Checks if the updated_at was set to a different value that is less than the saved value.
  # Raises ActiveRecord::StaleObjectError like Optimistic locking update.
  #
  def raise_if_stale_object
    if updated_at && updated_at_was && (updated_at.to_s(:db) < updated_at_was.to_s(:db))
      raise ActiveRecord::StaleObjectError,
        "Attempted to update a stale object. Record was last updated at #{updated_at_was}"
    end
  end

  ##
  # Overrides update, could not be a before_filter without setting record_timestamps to false and reimplementing timestamping.
  # This is because the update_with_timestamps is called before update_with_callbacks.
  #
  def update_with_stale_object_detection(*args)
    updated_at_locking_enabled? && raise_if_stale_object
    update_without_stale_object_detection(*args)
  end

end