task.rb

class Task < ActiveRecord::Base
  after_save :sync_with_external

  def sync_with_external
    response = External.sync!(id: self.id, info: self.info)
    if response.error?
      self.errors.add(:base, "There was a problem, etc ...")
      raise ActiveRecord::RecordInvalid.new(self)
    end
    true # I still do this out of superstition
  end
end